Should I help my sibling/family or should I fight for myself first?

I got a disorganized family (I'm kind of the only parent here, not overreacting) and I don't want my sibling to suffer as much but I also need to take some time (a few weeks, even months) to finish something. I'm dwelling what should I do. Putting myself first seems like an obvious choice but at the same time it feels like betraying them and just so wrong, on the other hand, if I help them now, it could postpone something and make a domino effect of postponing other things which I don't want.