D; I just can't stand children. Look, I'm not gonna murder her, but I would rather her just not be around. 

Then they have a fight...

B:She's my sister! Come on! What's with you?!
D: she's annoying! Geez, can't you just deal with the fact I don't like her?
B:But why?!
D: Why the hell should I tell you?!
B: So there is a reason!
D: Urgh! Just leave me alone! 

Then Blake goes to Andries to ask what is Deamion's deal
A: Ah well....It has to do with his family. 
B: His family?
A: Right? He would never tell you, but he wasn't exactly raised the best.
B: Bad parents?
A: No parents, his brother raised him...if you can call it raising..