I had a friend once who, like you, had essentially played mother to her younger siblings. She now lives in Australia — a long way from their native Peru — and lives quite a solitary life.
I asked her, once, if she wanted to have a family and she said, “No, I’ve already been a mother for my brothers and sisters. This life is for me, now.”
I think that, maybe, when you’ve been through a lot together, there is nothing left to say, being together is just a reminder of the bad times and it’s just time to live for you.