My parents sat myself and my brother down at 15 and 12 respectively.
My dad was in a right state, my mum putting on her strong face (although we didn't know that)
They didn't tell us it was a permanent split, because unbeknown to us, my dad had threatened to kill himself and so my mum had had to talk him into just giving her some space.
We wasn't told the reason, as my mum thought my dad should be the one to tell us and he was too cowardly.
He had cheated obviously.
I guessed eventually, but it was very bewildering (to put it mildy) at the time. My younger brother hated my mum for quite a few weeks until i eventually realised he blamed her, cos all he could see was my dad crying and my mum keeping herself together for us. I told him in the end.
It was tbh, a right mess of a way of telling us.
We are both extremely close to our mum. Our relationship with our dad has never recovered. I see him on special occasions. My brother even less.
Thought i'd just share in case it helps to see how not to do it.
They are younger than we were, but it's very confusing to see your parents split up without an explanation. They really really need one imho.