Can't see my grandkids

My and grandkids mother are no longer together. She keep the kids away from me when she get mad at him i stay out of there disagrement but she wants me to dis own him or punish him . He is a grown man i dont wabt to be involed in there frude.So speeks bad about us but we dont say bad things about her. She uses tge kid as a weapon. Me as a grandmother only wants to love them. What can i do