Who is more deserving of dutifulness: the biological parents, or the paternal uncle and aunt who raised the girl, given the parents' desire for the girl's return and the cousins' refusal of that?

The rights of parents come second only to the rights of Allah, and no human right supersedes them except the right of a husband over his wife. While your paternal uncles who raised you have a great right over you, it does not reach the level of your parents' rights. Therefore, you must obey your parents by returning to them. You should not forget the kindness of your paternal uncles and should continue to maintain ties with them as much as you can. As for your paternal cousins, if there was no prohibitive suckling, they are considered non-mahram to you, and it is not permissible for you to be in seclusion with them. You must also observe hijab in front of them.