I'm not going to help my sister move
Why aren't you going to help your sister move?
Because I have to move too, and it's going to be a real pain in the ass to help her. I don't have time.
You should help your sister move. It's selfish not to help her since she's family.
Did you see my new apartment? I'm getting it from my parents. I'm expecting them to help me.
See your parents are giving you a hand so it is nice to have help from a family member. You should do the same for your sister so she can feel the same.