Under their Parents, press What are you trying to fix? and choose the option saying a parent's relationship to them is marked incorrectly. Families grow in all sorts of ways! You can choose birth, adoptive, step, foster, guardian or raised by. For example, if your uncle was adopted by Jean and Bill, mark them as his adoptive parents – and his birth parents can be on the tree too, if you know them.
Where to find it
Person page (Safe edit on) → under Parents, Partners or Children → What are you trying to fix?
Only people with the "Add people" and "Remove" ticks, with Safe edit on.
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