Newt and Tina got married after the Grindelwars ended, and decided to travel the world together for a bit, Newt's job requiring that of him a lot of the time and Tina having trouble stomaching the corruption of MACUSA Aurors she witnessed up close. After exploring the world and even living in the USA for a few years, they eventually decided to settle down in the UK, where some of Tina's family already lived (Anthony Goldstein is apparently canonically related to her) and where there were less strict laws about separation from muggles in case any of their children turned out to be Squibs or wanted a relationship with a muggle like Queenie and Jacob had.

They had children quite late, with their eldest being Lacerta "Lacie" Scamander (named for the lizard constellation since there seems to be lizard theme with Newt and "eyes of a salamander" which are lizard-like amphibians) who was born in late 1958 and their other child being Caladrius Scamander (named for a mythological dove that appeared at the bedside of sick people, taking their ailments and flying away to cure them) who was born in early 1960, making the two of them only one school year apart. They were very close growing up, and Lacie was a rambunctious outgoing person that reminded them a lot of Queenie while Caladrius was a more shy kid that reminded them more of Theseus. They both still cared very deeply about the environment and justice, and Lacie hoped to become a environmental conservationist while Caladrius wanted to work for the Ministry, changing legislature to create more protection for creatures. They're also obviously both autistic and Jewish.

(I don’t really have any headcanons for it Theseus ends up married and having kids, so that’s why he’s not really getting talked about, although I’m down to make that a thing.)

When they got to school, they were both sorted into Hufflepuff and Lacie was somewhat offputting to a lot of her classmates, so it wasn't until Caladrius began attending school that she really had any friends. They also made friends with Quirinus Quirrell, who was in Caladrius's year and similarly shy and nerdy, with an interest in muggle culture and dark magic. An odd combination but the two of them thought he was cool.

Once trouble started brewing with Death-Eaters, most of the Scamander's didn’t really plan on joining the fight, Newt and Tina having already fought in a war and lost so much, and Caladrius not interested in violence. Lacie was the only one who decided to join the Order, while Caladrius had moved to Argentina and fallen in love with a woman named Esmerelda Vargas — a botanist who worked in cultivating endangered plant species — where he planned to stay. It wasn't until Walden Macnair had killed Lacie that Caladrius returned to England with his pregnant wife, hoping to stay and help take up the mantle of what she'd being doing. Voldemort was defeated shortly after though, and people were celebrating before the Scamander's even got to have a funeral for her.

Caladrius went to the trial of Walden Macnair and tried to explain that when they'd been in school together, the boy had taken great joy in tormenting people, and that it came as no surprise he would target Lacie Scamander. Walden was obviously found innocent of his crimes, claiming to have been under the impacts of the Imperius Curse, and wound up working alongside Caladrius Scamander in the Department of Regulation and Control of Magical Creatures, specifically as an executioner for the Committee for the Disposal of Dangerous Creatures, the exact subsect Caladrius was trying to have abolished.

When it came to legal issues, Caladrius and Walden continuously butted heads, and people stopped taking Caladrius as seriously because they assumed he was only arguing for the sake of Walden killing his sister while Imperius'd and insisted he needed to "get over it" and "forgive Walden" because "he's a victim too". Esmerelda faced similar scrutiny when it came to the protection of endangered plant species, because a lot of people thought of her as nothing but a "foreign farmgirl who doesn't understand urban life".

They raised their two sons, Rolf and Wren Scamander (Rolf is canon, Wren is an OC) on a farm with vegetable anf fruit gardens, chickens and cows, and while Esmerelda was a vegetarian the rest were not (until Rolf eventually went vegan as an adult). Rolf and Wren looked a lot like Esmerelda, sharing her thick curly hair and darker complexion (Rolf is canonically described as "dwarthy"), but Wren grew up to become a Squib.

Caladrius and Quirinus had stayed friends for the most part, and Caladrius found great comfort in confiding in his childhood best friend about the loss of his sister and mistreatment at work, but Quirinus eventually began acting strange. He disappeared for a year, going on his own travels, and Caladrius had been quite happy for him, if very concerned by his odd behaviour. When Quirinus returned, he was acting even stranger, with more anxiety than when he left and a new position as the DADA Professor, which Caladrius didn't think was a good idea with how unwell he seemed to be. It wasn't until he got the news that Quirinus had died by the hands of Harry Potter (literally) that he found out his best friend had planned to resurrect the very man in part responsible for Lacie's death. He was heartbroken and betrayed, but more than anything he was desperate to know if Quirinus really had turned evil or if he'd just been a victim who desparately wanted to get Voldemort out of his body. He felt immense guilt over the idea that Quirinus maybe didn't seek help specifically because he heard how Caladrius talked about Walden. But he would never know.

The death and public dislike for Quirinus Quirrell was also quite upsetting. How was it that Walden Macnair, a murderer who could not prove he was under Imperius and who now killed creatures for a living, was allowed to walk free and continue his cruelty while Quirinus Quirrell, a scared man whose body was being inhabited and killed zero people, was a worse villain? Caladrius hated it, and he disliked Harry Potter and what he stood for because of it. He became very cold, and this greatly impacted his relationship with his two sons.

Rolf and Wren remained close, even as they went to separate schools (the very next year for Rolf), with Rolf being a moderately popular Hufflepuff at Hogwarts, friends with people like Hannah Abbott, Ernie Macmillan and Sally Smith, while Wren went to a school for Squibs, that while it wasn't good, it was the best option aside from just throwing him in the deepend at a muggle school.

Rolf heard rumours of the Heir of Slytherins Monster, and wondered if it was truly a monster or just a beast who'd been mistreated, and would write home his theories about it, as well as the things that were going on at school. Caladrius and Esmerelda, being the cautious parents they had become, wrote to the school planning to pull Rolf from hogwarts until the issue was resolved, and Caladrius requested permission from the Ministry to find the creature and give it a more appropriate home. He was denied that wish, as they arrested Rubeus Hagrid and hoped that would settle the issue. When Harry found the beast and killed it, the Scamander's were not happy to see such a rare and misunderstood creature killed for it's masters crimes while it had been trapped and likely starved for centuries. Rolf never ended up having any strong feelings about Harry himself, but he heard his parents complain that their so-called saviour did not deserve the heroic praise he was getting, although Rolf was all too aware that Harry was only a year or so older than him, and couldn't possibly be that bad if he was just a kid.

The next year, Walden and Lucius teamed up to have Buckbeak executed for hurting poor sweet Draco Malfoy, and this was the year Rolf decided he thought Draco was probably one of the worst people in their school. Wren on the other hand was having a fairly normal, if somewhat bigoted, experience at school, learning about how to exist between worlds while studying a variety of subjects that interested him. He felt a little out of the loop, but he was also a little thankful he was so separate to the issues his family were dealing with. He also made friends with Douglas Barclay and Aria Herzenstein (headcanoned Squib parents of Sophia Barclay) who were two years older than him, but very cool. Even if Douglas in particular got into a lot of trouble (he came from a bigoted pureblood family that was ashamed of him while Aria came from a half-muggle family so she had little issue adjusting).

Years continued, Rolf joined the Quidditch team, the Scamander's heard of Voldemort's return and chose to side with the Ministry, whom insisted Harry Potter was a liar, for the sake of not liking him. Rolf and Wren thought this was a little petty, and Wren, being a Squib, was very concerned for his safety, while Rolf had met Harry a couple times due to being in Dumbledore's Army and didn't think he was that bad. Rolf also met Luna Lovegood during this time and fell head over heals because he thought she was the coolest person in their year.

During the events of Deathly Hallows, Rolf would've been in his sixth year while Wren was in his fifth, the Scamander's were attacked and Walden Macnair invaded their home, alongside Rabastan Lestrange, wanting revenge for Caladrius's always contradicting him in meetings. They also planned to taunt him a little bit about Quirinus Quirrell. There was a housefire and Esmerelda died, while Caladrius and Wren got out, unable to find Rolf, who'd also escaped but couldn't find the rest of his family. Rolf ran away and went to Hogwarts, rejoining Dumbledore's Army under the impression that his entire family had been murdered, while Caladrius and Wren ran away to Argentina with the Vargas family, believing Rolf had died in that fire alongside Esmerelda. It wasn't until the Battle of Hogwarts, where Rolf fought and was attacked by Fenrir Greyback before being saved by Lavender Brown (who died shortly thereafter) that Caladrius and Wren found out Rolf was alive, due his name, along many others, appearing in the newspaper as now being a werewolf (headcanon based on his name meaning "wolf" and Luna's name meaning "moon". Like Wolf marrying Moon and you expect me not to make werewolf headcanons?).

They reunited, and Walden Macnair was finally brought to justice. Rolf thought about joining the DRCMC like his grandfather and father, specifically because as a werewolf, he was now impacted more than anyone else in his family, but chose to become a veterinarian for creatures instead, not wanting his curse to take over his entire life. Wren ended up becoming a teacher, wanting the education for squibs to be improved and hoping that Squib students would finally get to have a role model that was actually one of them, instead of just a muggle-born or pureblood that wanted to help but didn't quite understand.

Rolf and Luna ended up meeting a variety of times over the course of university due to being in some of the same classes, and hit it off. Rolf was down bad, and Luna was oblivious to it all, although she also really liked him. When they finally started dating, Harry Potter, the very boy Rolf grew up hearing was a false hero, instantly had beef with him because he was very protective of Luna. Meanwhile Rolf was just very confused because, sure, his parents didn't like Harry, but he'd never said anything rude and he'd always silently thought his parents were a little too harsh on someone who was barely any older than him. That beef mostly went away after a year or so of being in a committed relationship, and it mostly turned into a friendly rivalry. Rolf also has beef with no one on account of being vegan.