You and Grace have five kids, you and Simon have two, and three adopted pebbles that your three have taken in.
All three of you act as parents to all ten children and they are all raised like fully siblings together. There is no such thing as “half siblings” in your household just because some are born from you and Grace and others are born from you and Simon. Obviously the pebbles are acknowledged as being Eridians but they are still raised as part of the family.
Rocky and Adrian are godparents to all of them and your respective children are all raised in a vague sibling-like way where Rocky and Adrian will help raise your children and vise versa. This can be Rocky and Adrian being part of the polycule if we want to see it that way. I don’t know how family labels work on Erid, so to Earth the ties are a bit confusing.
You and Grace have miraculously had all girls. It’s a little mindboggeling that you two birthed five baby girls in a row but Grace doesn’t mind one bit!
Their names are Olesya, Mary, Cassiopeia (aka Cassi), Ursa, and Artemis (aka Missy). Born in that order by the way.
Grace planned to name his first daughter and son after his fallen crewmates. He fully planned to implement Yáo’s name somewhere in the naming of your hypothetical future son after Olesya was born… but then you had Mary… and the twins… and then Missy…
Grace isn’t continuing till you and him have a boy together or anything… you just… do it a lot and sometimes a baby gets made, and they keep being girls. Again, Grace doesn’t mind but at this rate it’s like some kind of gag the universe keeps doing and it’s honestly kind of funny.
Cassi and Ursa are identical twins and were almost named Gemmi and Emmi to make a Gemini constellation reference, but he decided that matching twin names were stupid and robbed them of their individuality, and so chose the constellations Cassiopeia and Ursa Major instead. Grace, you, and later Simon are able to tell them apart perfectly even before they gained their individuality and personalities and have no discerning birthmarks. It’s very confusing when you visit earth and people keep mixing them up.
You and Simon’s two only children are also twins but unlike Cassi and Ursa, they’re fraternal twins and consist of a boy and a girl. Their names are Adam and Ivy.
Grace didn’t pressure Simon into honoring Yáo since he believed that it was Simon’s right (yours too) to get to name his own son and actually thought that Simon naming the first boy born on Erid after Adam from the bible was cool. Ivy is named after the plant after Simon learned about them being a symbol of endurance and rebirth on Earth because she and her brother have managed to come into existence despite everything being pitted against Simon and thus them.
Ivy was born first, which means that she’s slightly old than Adam and her and the rest of her sisters tease him with it and treat him as the baby of the (human side) family.
They have a few fish attributes due to Simon’s mutations ending up in their DNA but they’re perfectly healthy and have even embraced most, if not all, of their traits. They did have a serious biting problem when teething thanks to them developing sharper teeth. The biodome team had to find materials safe for them to chew on in order to help them through it and later on had to adapt the shore part of the biodome to be larger because they really like being in the water. If they aren’t in their normal spots on land then they are definitely in the water swimming and diving around. It’s like that one audio with Undyne’s theme and the voice over going “I need to touch THE SEA! I NEED TO GO IN THE WATER!”.
The pebbles are all adopted and are either orphans/abandoned or have issues that leave them at a disadvantage. Eridians do adopt too but sometimes certain birth defects and disabilities make it hard for pebbles to make it past pebblehood. So you, Grace, and Simon take them in and foster them till they can overcome or adapt with them. You never let them feel like that though.
Tiri (short for Tiramisu) gets her namesake from looking like the dessert. She’s the sweetest little thing but she has a brittle carapace that makes her very fragile. Blows and mishaps that Eridans can often tank are very detrimental to her. She uses a xenonite suit to act as a secondary carapace so that it’s the one taking any accidental hits or bumps instead of their body.
Go-go has crystalline structures on/in their carapace that will reflect light, causing a disco ball effect. They’re full of life but the structures in their carapace make it hard for them to pick up vibrations and echolocate in order to navigate around (meaning they’re technically half blind and hard-of-hearing). But you, Grace, and the biodome team managed to figure out how to make something to help them with that, and its also shared so that pebbles burn with the same defects can live life just fine.
David is the recent addition, Simon actually named him. He was born the runt of his clutch, with one leg missing and another shorter than the other three, so he walks with a heavy limp, which slows him down and makes his balance uneven. He was actually the most sickly pebble you all had received, to date. It was even mentioned that he might not survive long after hatching. You and Grace obviously took care of him, but Simon cared for him the most.
Simon would spend a lot of his time encouraging David to eat and checked on him till he came into better health. Simon had actually created a little prothetic for David’s shorter leg to help even it out and work out how to move with it. Simon’s very proud of him and makes sure to create a new one every time David molts and grows so that he can keep walking around and work with no issues. Though with how fast David keeps molting you guys are going to have to change his name to Goliath! 
