The More I Think About It The More I Realize That If This Guys Had Met Under Different Circumstances,

The more I think about it the more I realize that if this guys had met under different circumstances, they would have gotten along super well.

PENACONY SPOILERS UP TO 2.2 + CHARACTER LORE / STORIES

All 4 of them have lost their entire family, 3 of them have lost their entire race / homeworld (Boothill, Aventurine, Acheron), 2 of them lost these things because they were victims of the IPC (Boothill and Aventurine), and 2 of them have either lost a sibling or are afraid of losing a sibling (Aventurine and Sunday).

More specifically:

As far as I know, Sunday and Robin's parents were killed somehow, and they were taken in by the Family. Then as Sunday said Robin ended up getting shot in the neck due to trying to help others, and I think he got some kind of trauma from that and his fear of losing Robin, his sister and only remaining family, was amplified, leading to his desire to protect "the weak" no matter the cost—because to him, keeping Robin's wings "clipped" and her alive would be less painful than her being gone, and him being alone forever.

Boothill, as I understand it, was taken in by 2 people who found him as a child, and grew up in the countryside of his planet. He later found and adopted a young girl and raised her as her own, until his entire planet was destroyed by the IPC, causing him to set out to get revenge.

Aventurine also lost his sister and his entire home planet due to the IPC + his planet's own problems, and has been forced to work for the IPC ever since. It also seems like he's trying to destroy it from the inside out or at least obtain his own freedom.

As for Acheron, her entire world, as well as her memories of it, were destroyed—she's almost certainly lost people that were important to her, like the other three.

Like honestly if they all sat down and traded backstories I feel like they'd get along super well, they're all victims of circumstance and that's why they experienced so much conflict during the story