Feel like I've lost a family

Found out last night that I have a great nephew, lovely in some ways, but not when you consider he was born on Jan 6th 2011.
I only found out because I mentione to dad that J had had a baby on the anniversary of my mum's death and he said well K's son was born on your mum's birthday. You could have knocked me over when he told me and then showed me the picture of him.
Dad said he thought he'd told me and then kept saying he hadn't told anyone for 6 months because of the circumstances - K was 2 weeks away from his 15th Birthday when his son was born.

I email my sister's, never get replies, ring and they are always too busy. I send cards for birthdays, Easter, Christmas etc, yet they never do, obviously they don't want to have anything to do with me and it hurts.

Thank fully I have some wonderful friends, a fantastic husband and children and that is as much as I need