Yes – there's room on the branch for both! When you add a second mother, the one already there stays exactly as she is, and you choose how the new one goes on: as a birth mother beside her, as a probable or possible mother, or as "not sure" (recorded as possible for now). For example, if your dad already has Jean as his mum and you find out Rose is his mum too, Jean stays put and Rose joins her. Two dads work the same way.
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