Sorry, you'll have to choose which family branch you want to delete, then go down to the lowest level of each person (child, grandchild, greatgrandchild,...) and delete each, one by one. Then delete the spouses. Then move over to the next couple and repeat.
Imagine a mobile, with the family members as hanging weights. You have to delete them from the bottom, up, until you get to the original duplicate person, then delete that one.
The rule is that you cannot delete someone that still has children under them, or their spouse.
