So often JWs, including our families, are taught that they will gain 'brothers, sisters, mothers and fathers' in the faith. JWs are encouraged to push away anyone not in the faith. Recently, I have had Facebook conversations with my aunt, who I haven't seen in decades. She did mention that my parents were always witnessing and it did get tedious. I reconnected with my cousins on FB too, as we live over a thousand miles away.
If you contacted your mom's family, they would probably realize that you didn't shun them, your father did, and by default your mother. They were probably missing your mom and her kids too. No Christmas's spent together, no birthdays to commemorate the kids getting bigger. 'Wouldn't it be nice if ___were here?' It isn't too late to TRY to connect with them. Until we are dead, it isn't too late.