You say that this man can’t express himself in normal sentences. But can he effectively say no? In your account, the man, despite his deficits and significant aphasia, also seems to have appropriate and coherent beliefs and desires: He knows he has a child, wants to see that child and grieves because that child has been kept from him. You don’t give us reason to think that, in a sexual situation, he wouldn’t be able convey the sentiment ‘‘I don’t want this.’’ For that matter, we don’t know whether he or the woman initiated the sexual activity.

I’m suggesting that sex involving the cognitively disabled isn’t, ipso facto, assault. I’m not concluding that what happened here was right. Even if the sex itself wasn’t violative, the man may not have been in a position to discuss whether he wanted to have a child with this woman, and therefore to think about contraception. If the woman knew this, she wronged him. (You don’t discuss her motives here, except to say they don’t have a relationship. If she had been trying to get access to his resources — his financial situation is comfortable, you say — this would be a further wrong: exploiting another person’s vulnerabilities to your own advantage.)

A second question is whether she should allow him to see the child more often. That he’s heartbroken not to see his offspring more isn’t the only relevant consideration. There is also, centrally, the issue of what is good for the child and reasonably convenient for the mother. Because he sees the child sometimes, the mother presumably doesn’t think that the visits are harmful; it would probably be kind to permit more. Whether it would be easy for her to do so, I am not in a position to judge, and perhaps you aren’t, either.

None of this settles the hovering question you didn’t ask, which is what, if anything, you should do. Do you have sufficient connection with these people to be entitled to intervene in their lives? How sure are you of the facts here? Would it do any good to the child or to his father to have the mother charged as a sex offender? Do you have the standing with the mother to urge her to allow the father more time with the child?

Here’s a suggestion. You know about these events because you and these people belong to the same church. Wouldn’t it make sense to bring these questions to your pastor? He or she could then take up with the child’s mother whatever concerns seemed appropriate.