Matters not, they can bring charges whether the mother is deceased or alive. It's very possible that they might could have brought charges against HMR's parents, had they been alive. I don't think there is a parental consent clause, in any state with consent laws, so, if that be the case for OH, a parent who gives consent to their minor, could be prosecuted for child abuse.
They could do the math in family court, prior to HMR's death. She got pregnant with S, around six weeks prior to age of consent, (around mid - Feb, 2013), after a relationship that started 8/27/2010, according to HMR's Twitter feed. As far as we know, that's the only time they had relations, well, til he thought he might be K's father. I'm not saying that it was the only time, but it's the only time that we have proof.