Mostly No! A sibling or a parent have the moral right on your money according to me...in a more old-fashioned and family oriented way that is. Asking them to 'return' the money they 'owe' you could cause a problem in your relationship.
However, if there's a proper understanding, ie., if you both can talk about money borrowing and lending in a casual way, its good to ask.
All in all it depends on how mature is that person, do he/she take personal/ money issues personally; then its safe not to ask. And if they're broad-mined enough, then what's stopping you?
Lastly, it also matters on what were the circumstances that lead you to lend your money in the first place!!