I don't in any way condone Woody Allen's behaviour with Soon-Yi Previn. I think he behaved disgracefully, both with her and towards Mia Farrow and their massive complicated brood of children/stepchildren.
But this is a very unusual family set up.
Mia Farrow married Frank Sinatra when he was 50 and she was 21. So she knows all about the power imbalance between older and younger partners. She married Andre Previn when she was 25 and he was 41. Their relationship began while he was still married to Dory Previn. He left Dory because Mia was pregnant. (Mia claims to be a devout Catholic, btw.
) She took up with Allen shortly after splitting up with Previn and never married him, nor lived with him.
In all she has 14 children, 10 of whom she adopted, in some cases jointly with Previn or Allen, in other cases as a single woman. Three of the adopted children have died early in adult life. Moses Farrow claims that two of the deaths were related to addiction. The third was suicide. After the acrimonious end of her relationship with Allen when she found about his sexual relationship with Soon-Yi, she claimed that Ronan could be Frank Sinatra's child as they had never really split up.
None of this strikes me as indicative of a healthy, happy family.