I'm doing extensive research (kinda exaggerating tbh) on Strangetown by taking notes of all the personality/personal stuff of each premade in vanilla Strangetown. I have many thoughts that I'm probably going to turn into posts later, but I wanted to talk a bit about the Smith family, specifically Johnny's and Jill's relationship.
When I start the game, Johnny has a 20/20 relationship towards Jill, and a 45/45 towards both his parents. On the other hand, Jill has a 48/20 towards Johnny, which is similar to her daily relationship towards her parents (44/35 jenny and 45/35 pt9). That is a big difference. The only other canon interaction I could find is the Smith's thumbnail, in which Johnny is giving Jill a noogie. I'm not sure if this is scripted behavior or only happens in my game, but starting the game Jill tries to hug Johnny and he rejects the interaction.
Now, what does this mean? Maybe nothing. But I found that answer boring. One interpretation is simply that they are not that close because Johnny is quite a bit older than Jill. It's normal that siblings with a large age gap to be kinda distant, specially if Johnny is a teen who might see Jill as annoying while Jill may idolizes Johnny because he's her big brother.
Another interpretation that can complement the first one is that there might be a bit of jealousy going on. It's stated in the family bio that one of the central themes of the family is Johnny's social life and whether he will fit in or not. Johnny is clearly half alien, but Jill isn't. I wonder if Johnny might be a bit jealous of Jill. She can hide her ancestry, but he can't.
Another layer of the jealousy might be Jenny. We know by her bio that she wishes she had more time for her family, and she has a want to quit her job at the beginning of the game. Checking the family memories, Jenny was already working when Johnny was born, and she didn't teach him any skills. But she taught Jill how to walk. It seems to me that Jenny might be trying to compensate that she wasn't as present as she wanted in Johnny's childhood. She has 2 wants and 1 fear revolving around Johnny at the start of the game (Johnny grows well, hug Johnny, Johnny has a lousy party). And she might want to quit her job so she can focus on Jill (and the rest of her family). Maybe Johnny (even though he clearly doesn't seem to resent Jenny) can see that she's trying to be more present now, and wishes he could have his mom be more present as Jill is.
This is not to say that Johnny hates Jill or that Jenny is a bad mom. I think Johnny loves Jill and wishes her the best, but he might be a bit hurt that she has a more present mom and no clear alien traits. And Jenny is a wonderful mom doing her best to balance her career and family life. The Smith's still are the most wholesome family in Strangetown, but I think they're not as perfect as they appear at first sight (no family is perfect).