My Nan C would've been in her mid 30s, I think, her first grandchild was born a year or so after my mum I'd never really thought of it like that! She was 55 when she became a great-grandmother, 75ish when she hit great-great.

Nan M... I have no idea, because I'm not sure when she was born or how old my oldest cousin is on that side I'm going to guess late 40s, possibly mid 50s. All her kids were close together and the older ones had a later start having kids than the younger ones, so almost all the grandkids were born in the span of ten years or so.

My mum was 46 when Ianto was born, 47 when Amelia was born (for those who refuse to count Ianto)