Theory.
Lana and Jill are sisters, Amelia is too old to be Lana's mother and Jill's genetics don't match Amelia's, but the Madame's genetics do. The Madame is Lana's and Jill's mother and ex-wife of Jill's father, who is not Lana's father. Lana is a cuckoo child, which old Royce found out years later. Old Royce divorces the Madame (Monica), fucks all the women he comes across for a while, and eventually falls in love and marries Amelia, with whom he has another child. I have no idea yet who this could be. The question I have is, during his I fuck all the women phase, did old Royce impregnate any other women? The however exciting question is when did old Royce find out that Lana was not his daughter? What if this all happened when Jill was a baby?