Ugh...where do you want to start?! My situation isn't steps, though. Dh and I have 3 bios- DD1, DD6, and DS4. SS13 is their half-brother. I can't explain the difference either. My bios get along wonderfully MOST of the time. Yes, the argue and physically fight at times, but they are also 'best friends' and don't hold grudges. After a fight they'll cool down and play again and snuggle with each other at night. But with ss, things are different. They hold a grudge almost and won't want him over because they'll remember last time when he picked on them. When my bios argue I help them work it out. When ss picks on or fights with my kids I want to wring his little neck! (of course I'd never lay a hand on him, but it just make me so mad!) I told my mom once that when the bios fight with each other there is still a love for each other inside and no matter how many times they argue, it always comes back to that love for each other. But with ss, that love is missing...both ways. My ss didn't visit for 3 years. He missed 3 years of our lives and we missed 3 years of his life. My bios didn't get to bond with him. When he started visiting again last year, it was like having a stranger over. So when ss and bios fight it's different. There is no love to come back to. If ss picks on them I know it's coming from a place of anger, resentment, jealousy or whatever instead of just being annoyed. Hard to explain. I recently blogged about how when ss comes over, even my bios fight with each other more and I don't understand why. Anyway, that's my thought for the day. No advice. You'd think the big age difference between ss and my bios would mean leas fighting, but no.