I think Pedants' Corner is the right place to ask this. There's something about the expression "mum to 3 boys" or "mum to George and Molly" that grates and I don't know why. It's that word "to".
Surely, the standard usage would be to say "of", as it's a relationship, as in "husband of the Prime Minister", "son of John and Mary", "brother of...".
The "to" seems a bit too earnest (?) or makes it sound like a job (?) or as if that's all that defines that person: "I'm just a mum to two small boys" (I suspect "I'm just a dad to..." arises less often). I can't quite put my finger on it. I feel like I first encountered it in trendy magazines aimed at parents, eg something from the NCT, but that would have been some years ago.
Do I just need to get over my hang-up or does anyone have any sympathy with my reaction?