The sooner you can seperate them, the better - before the roots get anll intertwined. I start pepper seeds every year, 2-3 seeds per plug. It’s the same deal, get them apart before the roots tangle up and then they’re fine.
I had this happen in my current run.
two tails popped out the hull before i sowed them.
One of them dominated and the other aborted growth, i didnt even get rid of it its just there doing nothing standing an inch above soil
This happened to me recently one was male one female. Wasn't hard to pull apart after sexing either just pulled the male straight out but I bet it would have been if I waited any longer.