From what you say above, under California law, Myriam is effectively guilty of rape herself, because Marc would be regarded as a minor there. She's applying for legal guardianship of him, which means he's not yet 18. Therefore, if she willingly has penetrative sex with him, she effectively would be raping him in California, and not just taking part in an incestuous act.
Nope, I checked when I looked again for the incest patch. Marc is agreeing, so it would no be rape, although given the age difference, would still be a fellony, and in the case of the incest patch, incest.
Incest covers sexual intercourse in California, and while having sex below age of consent, when even one of the two is under that age, is a fellony, it is not rape - there is no statutory rape in California, a bill about it was proposed some years ago, and was killed.
For the rest, that's where you starting to see the problem of taking the game too precisely/seriously
, a crime of which at times I am guilty myself
.
Zorlun said he decided later to make Marc 18, which would mean indeed no custody in California (safe maybe special situations, but that are not applicable to Marc).
But actually, if it was not her son, even if he was under 18, she would have no claim for custody, because they are not married (unless using the incest patch, and the original storyline as Zorlun had first made it).
At maximum, if it was decided to put him up for adoption, she could try to be considered as guardian as a kind of "foster care" situation, or to adopt him, but in general, there are families that are already part of the foster car system, and in a situation where Myriam and Anthony are fighting and they are not married (I am not considering jurisdictions were registered legal cohabitation is considered almost identical to marriage, because that does not appear to be the situation in California, nor in most USA States), no decent social support services psychologist would give a positive opinion to the kid being put in the middle of that conflict situation.
They would rather support him being put temporarily in a location and environment supposed to shield him away not only from Anthony, but also from the conflict between Myriam and Anthony (which would mean, if not Anthony, then not even Myriam).
Different matter in the situation with Myriam and Anthony being married (battles for custody over the kids are almost standard fare for divorces).
Of course, there is always the possibilty the judge was given very good argument by Myriam that made him see Myriam's very well developed arguments
, and/or being sucked irresistibly in by the truth
, and therefore decide for Myriam.
But we know that the whole sequence related to custody etc. was a plot by Zorlun to have a way to get definetively (aside one eventual episode in future, depending from the player choices) rid of Anthony, he even admitted he did not think too much about representing exactly the legal aspects, so, IMO we should not spend too much energy on that.