Only first books in series unless only a later book features the dynamic and the earlier one doesn't.
(If anyone is a librarian and could help me clear up the list, this would be highly appreciated!)

No, we don't always want an orphaned protagonist or a dysfunctional family.
This list is for all the books with loving families, siblings that would do almost everything for each other, functioning adopted families etc. It does not mean that they have to be perfect or that every person in the family is part of the good family dynamic.
Found family also counts if the people in question are in a family-like structure (adopted for example).
Most importantly, the family in question has to be ALIVE and the positive relationship has to exist throughout the majority of the book, best if it already existed before the book started (please no misunderstandings at the beginning of the book that get cleared up at the end or books where it is revealed at the very end that they did it for their best all along etc.)