Do you have any headcanons or analysis about Santana and Brittany's relationships with their parents, separately as well as a (married?) couple?
This is more headcanons since we didn't see enough of them in canon to analyze on its own.
The Lopez family - I see Santana as having a close relationship with her Abuela, before The Outing, and Alma being the one who basically raised her. I headcanon that both her parents worked a lot and that's why Alma acted as the primary parental figure. Santana's relationship with her parents isn't bad, as such, but I do see her growing a lot closer with her mom Maribel after she comes out and Alma disowns her. They talk through a lot of Santana's issues and Maribel makes more of a conscious effort to be there for her. Maribel's no-nonsense and she gives Santana a stern talking to when needed but she softens as their relationship grows. She realizes that Alma's toughness rubbed off on an impressionable young Santana in some not so good ways so she's more openly affectionate as Santana enters her twenties. I see Santana as needing words of affirmation as a love language, in all her relationships, so Maribel tries to meet that even though Santana never articulates that need.
As for Mr. Lopez? Anyone's guess, literally. Every interpretation I see of him differs because we get so little. Santana only mentions that he's a doctor once and then I suppose one could run with the implications in "Lights Out". Personally, I'd like to think Santana's dad isn't all that cold and distant but there's for sure a complicated dynamic there. He worked a lot, possibly only just finishing up med school after Santana was born, once again hence Alma raising her. He and Maribel both have a feeling from when Santana's young that there's something ~different~ about her, something queer. Mr. Lopez, based on his own upbringing, would rather pretend it isn't there. Santana internalizes this as there being something wrong with her and is absolutely mortified to be forced to come out to her parents.
But Mr. Lopez, having taken his sweet time, reassures her that there's nothing wrong with her and he and Maribel love her very much. It's just that he knew how cruel the world was and didn't want that for Santana, and didn't communicate how he'd accept her no matter what in the best of ways. He does some soul-searching after that and chews his mother out for disowning Santana. Like with Maribel, Santana's relationship with him is better after that but there's still work to do and imo they haven't done much by the wedding and it's mostly in Santana's later twenties and as Mr. Lopez begins to work less that they truly form a bond. There are many regrets but they both learn a thing or two about owning your feelings.
The Pierces - The Pierces are much more chill. They don't even register Brittany being bi as anything unusual. Whitney catches Brittana making out one day and just asks if Santana's staying for dinner. Both Whitney and Pierce are very open and loving with Brittany and maybe even a bit TMI. Sometimes it can be to Brittany's detriment because she has a harder time learning about ~normal~ social etiquette and what's appropriate but she's always encouraged to speak her mind. I am truly very sorry how comically short this is compared to the Lopez section but they really are just chill and somewhat odd.
As one big family - As mentioned, the Pierces (particularly Whitney) knows about Brittana and Britt's queerness long before the Lopez family or anyone else. She's cool with it to the point of not really registering it as anything differing from the norm. That kind of backfires when Santana's anxious around her after the interrupted makeout sesh, not knowing what Whitney thinks of her now. But they eventually have a big discussion and Whitney makes Santana sob with how much she loves and accepts her. Santana became a part of the Pierce household long before the wedding. (Ignore Pierce's joke from 6x06.)
Maribel found Brittany to be unnervingly odd at first but girl has a way of charming you so she was cool with Britt by the second or third time she came over after Cheerios practice. They have good conversations and Brittany always leaves with a shit ton of food made special for her. Mr. Lopez rarely interacts with her but just like with Santana, he makes more of an effort when they're engaged and married. They play chess together and rarely utter a word. It unnerves Santana and Maribel but both hate playing chess with their partners so it works out.
Whitney and Maribel have hilarious interactions at family dinners and gatherings. It starts out somewhat charged, from Maribel's end, but they both love their girls so much so really it's just playful banter by the time they're family. There's always arguments about where to spend the holidays so Santana and Brittany end up travelling to some random location on many occasions. One Thanksgiving they come home to find Whitney and Maribel wasted on the Lopez couch, apparently having had the time of their lives drinking together. Meanwhile, Alma is listening intently but with increasing concern to whatever Pierce is saying.
Bonus, Britt's little sister adores Santana.
