Is it obligatory to return stolen money to its owners, or to distribute it among the poor, if the owners' family disintegrated because of the theft, and they themselves stole a large sum from their relatives?

You must repent of theft. Among the conditions for repentance is to return the stolen money to its owner, or to return an equivalent amount if you have spent it. If you do not possess the money now, you are obligated to return it when you are able.

As for the theft from your aunt's house by her relatives, they must repent. If you know that the money you took does not belong to your aunt, then return it to its rightful owner. If it is impossible to identify the owner, then give it away as charity on their behalf, with the option for them, when they appear, to either have their money returned or accept it as charity.

We advise you to frequently seek forgiveness (istighfar) and perform good deeds.