Devil's in the details on this one.
First, the general inference seems to be all this took place in the DR, which probably has the following implications:
1) The DR has a general age of consent (AFAIK) of 18?
If there are specific "Romeo and Juliet" exceptions for parties being within a few years of each other across the age of consent line, I do not know them. Likewise,
if the DR isn't strict liability (where you can assert you were mislead and thus avoid liability), I don't know. So, criminal/civil liability in the DR will depend on not only the ages of the parties, but the law of that country.
2) Even given the written DR law (whatever it is) the social culture of the DR is not the same as the US.
3) Baseball is looking into this on their own and will make determinations that stand outside the criminal authorities reaction to the issue. e.g., Trevor Bauer. How much they will be swayed by the law/local culture of the DR is an open question.
So, really the devil is in the details. Their relative ages and the kinds of relationships they had at what points in time being the biggest things here, obviously.
I can see discipline issuing if the numbers look bad. e.g., he was >20 having sex with a 14 or 15 year old.
The asking for permission thing seems like it’s a red herring.
Does it really matter if the mother is
also a bad actor?
I suppose in a moral sense it goes to if he knew or should have known his girlfriend's age. But there I think, she'd have age-peer friends, attend a specific school, have or not have a driver's license, etc. etc. There's any number of ways one could know - this isn't alleged to be a one-night-stand with a 17 year old who claims they're 18.
I suppose it also might factor in if the mother knew the girl was technically underage - 17 years, 9 months, and approved anyway. But the alleged facts are nowhere near that.