My brother’s fiancée has a little boy from a previous marriage. When my family found out, they immediately freaked out and pushed her to sign a prenup — one that basically said her kid gets nothing, and only the children she and my brother would have together would ever inherit. They said it was all about “protecting the family legacy.”

She absolutely lost it — and honestly, I can’t blame her. But then, in the middle of all the yelling, she suddenly shouted something she clearly didn’t mean to reveal:
“Why are you acting like he’s not his son too?”
The room froze. Everyone was shocked. My mom’s face dropped like someone had unplugged her brain. My dad kept chewing, slowly, as if his mind just refused to process what he’d heard. And I stared straight at my brother — because suddenly, everything made sense. The weird little ways he watched the kid. The protectiveness. The excuses.
That’s when the truth came out. They’d had this chaotic, on-off relationship years ago. She found out she was pregnant during one of the stretches when they weren’t even speaking, and when she told him, he straight-up vanished on her. Ghosted. Years later, when they crossed paths again, he insisted he wanted to do the right thing — to be a father, but gradually and quietly, so it wouldn’t confuse the boy. They agreed to keep it a secret for now, letting the kid believe my brother was just the “stepdad.”

She was furious. She accepted that arrangement. But the prenup? That was her breaking point. She said her son would be protected — with or without everyone knowing the truth.
Now my future sister-in-law is angry at everyone — at my family for only caring about the child once they realized he was biologically “one of us,” and at my brother for not warning her about the prenup nonsense in advance, even though he knew it was coming.
And me? I’m stuck in the middle, wondering if I messed up by agreeing with my family at first. I want to confront my brother, but I’m terrified that bringing it up will blow everything up even more.
What am I supposed to do here?