Would you tell?

My now ex best friend has been going through a downward spiral. He has some mental issues, so when he goes through an episode he can make some pretty awful decisions. He does things to push people he loves away, makes choices that put him in bad situations or potentially harmful situations, etc. Up to this point, though he’s always had boundaries about how far he’ll go for it. I’ve learned it’s best to offer what help I can, push him to get back on his meds and go to his therapist, and then leave him be for a while for my own mental health. He’s never done anything that couldn’t be undone or forgiven.

Welp. Now he has. And he’s told me, which puts me in a position where I have to decide if I keep it in confidence or tell.

He slept with his brother’s fiancé. He KNEW they were engaged and trying to conceive. And he did it anyways without protection. On purpose. His brother doesn’t know. He thinks the baby is his.

To add to this— the pregnant woman in question should NOT be a mother. She has a toddler at home now that I personally have called DCS on multiple times. She does drugs and drinks until she passes out while he’s home, he goes days without eating— it’s not a good situation. She was pregnant before and that baby was removed from her before she left the hospital because it was born addicted. She gave up her rights and put that baby up for adoption. And now there’s this baby, and she’s already said if they try taking this baby she will not sign rights away, they’ll have to force it.

He knows she’s like this, he’s even reported her for her parenting and is constantly remarking that she shouldn’t be a mother.

His brother cares for her while she does this and tries to care for the kid, though he’s clueless as far as raising kids goes.

So the question is.

Do I tell his brother? If I do, he will leave and demand a DNA test. And if it’s not his, he will leave it with her and never look back. He deserves to know, but this could potentially leave this baby alone with her.

My friend has NEVER wanted kids, and has already said he has no intent on playing daddy— even if the kid ended up being his. He’ll pay child support but wouldn’t want visitation or even to meet the kid.

So this would end up putting the child already in the home without anyone, plus this baby alone with her.

If I don’t say anything, this baby will still have her as it’s mother, but at least the brother will be there which is better than nothing. But he will be raising a baby that’s potentially not his.

What do I do?