I agree with oldsoldier, let it go. Your deceased buddy told you this because he needed to vent, not because he wanted you to take some action. This is entirely her call.

From a woman's perspective. .

I think I'd let it go too. . . and of course you will get a why.

For some reason this woman chose not to involve this man with this boy -- maybe not even financially (which is odd for this day and age). While there were plans to do so, there may not have been plans for this to be a "family unit". He may have simply been a "natural donor to the cause". (Not that THAT has EVER happened!)

So let's say you go to your friend's parents and tell them of this conversation. Their son had a relationship with this woman and there is a child. This child may in fact be the only living legacy left of their son. But you don't know this woman, you may not know her name or where she is. They might know her or not. If we don't know this person, how will they ever go about finding her. Then they will sit there and stew about this long-lost grandchild.

or

Let things take their course and someday maybe the mother or child will find them. . . and they will have a wonderful surprise actually in front of them that is their son's living legacy that they can hug and hold.

And one more thought. . . . there might be one other reason this man wasn't introduced to the child earier or asked for support or whatever. A DNA test might prove otherwise. (Not that THAT has EVER happened) I would hate to put his family through all that turmoil. I can't imagine the family scouring the countryside for the long-lost grandchild only to find out later that it truly wasn't their sons. Toooo crushing.

With your friend's death, your involvement in the matter ended. Leave it be.

You should take comfort in knowing that your friend had enough trust in and respect for you that he confided in you something very personal and sensitive.

If he wanted the matter known to anyone else, he would have told them. He had plenty of time to do this.

Don't violate the trust he placed in you, and do not burden your conscience further by thinking you adopted his responsibility/accountability for the matter. You fulfilled whatever obligation you had simply by listening to your friend and being there when he needed someone. That is done now. Anything more you make of it is self-conjured and unhealthy, and further action will not be productive.

+1 to let it go.

If you don't know the woman, even her name, you can't develop any sense about folks' interests in making connections. It's part of the tragedy of his loss. Let it go.

Even if you do know the woman and could contact, I would STILL let it go.

Clearly you cared deeply for your friend and I am sorry for your loss. And perhaps this sense of wanting to "do something" comes out of that sense of loss you feel. But with all the caring in the world I mean this...

...it is not your affair and you getting involved is hubris, not love.

Let all involved mourn and move on, and what happens naturally happens.

1+

and then there are the unintended consequences.

+1 to what Art in Fla said. At most, I would try to let the woman know he is dead, since you don't know if she even knows, then leave it at that.

I said earlier that I needed to think about it. That thought was with a Legal Beagle I built a house for.

His advice was to act as though you never knew about it at all.

Agree. Honor your friend by maintaining his confidence.

Nothing is gained by stepping into something like this. Not for his son or his family. If he wanted everyone to know he would have said something before. If the boy's mother wanted everyone to know she would say something. Either way, keep your nose out of it.