why do they treat us like this

Have started to write this several times but really don't know how to do this.  Our story is  long and complicated so I don't want to muddy the waters at the beginning.  I just know that I have never been so sad and alone.  My husband is wonderful and tries to help but tells me to put all of this stuff behind us.  As a mother, I just can't seem to do that.  We've had problems for about the last 4 years but this is the worsts it has been.  He is the custodial father to the 3 oldest children.  Some how he has talked against us so that now our grandchildren don't want to have anything to do with us.  From the time he left for the Navy at 17, until he was about 32, we helped monetarily, emotionally, and physically.  A couple of years ago, he called and said that things weren't working out at his girlfriend's home and he needed to get out of there..  Before evening they were living with us.  As an only son and I a previous widow, we were always so close.  Now he has totally turned his back on us and won't even allow us to see the Grandchildren.   He should know my new husband and I better than anyone and we have always been kind and loveable to him.  About 2 years ago, we decided it was time for him to take responsibility for his situation his he and girlfriend were living together again.  They have 2 children together.  Since then he has been emotionally distant.  He has chosen to believe ugly rumors about us and then turned his back on us.  Girlfriend has a huge family which is appealing to his children.  We are not allowed to have any contact with our grandchildren.  We always had them over for Thanksgiving and Christmas as well as any many, many other times.  My heart is totally broken and I feel some one has ripped everything out of me.  Never did I think something like this could happen.  I feel so sad, alone, confused and hurt.  I want and need to become part of your group since I don't know where else to turn.  Thank you.