I've never met my grandmother.

Andrea • Est. 1994. Engaged. Mummy. Animal lover. Rugby lass.
This is a very difficult decision! 
I've never met my grandmother because my mum's parents divorced 23 years ago and it was a nasty battle (apparently) hence why we've never met her as my mum doesn't want us too! 
But i feel it's not fair as they are my only living grandparents (my dad's parents died when he was young). Both myself and my sister are adults and I have my own family. My son has so many grandparents (step families) and great grandparents! And I feel like I've missed out, but I've decided I don't want to regret never meeting my grandmother, I want to know her before it's too late.. but I know it will upset my mum as she feels I should be loyal to her and my grandad.
This choice wasn't mine, it was my mum's to stop her seeing me and my sister. Yet my grandmother has tried over the years with Birthday, Christmas and Easter gifts, yet they've all been returned by my mum! I know it would hurt my mum, but I've always been curious about my grandmother. 
Am I being selfish wanting to know my grandmother?