Childrens rights

I live in Clevland Ohio. I have a daughter who lives in the Houston Texas area. She has 2 children by a man she never married. They separated years ago and have never legally done custody agreements. Her daughter lives with her and her son lives with his Dad. There is no legal custody or child payments. They just take care of them jointly. Financially. My daughter has since gotten married. Anyway, here is my question. My granddaughter, who will be 14 soon. Wants to come to Ohio and spend part of the summer with us (her Grandparenst) Her mother, thinks this would be good for her. We would pay all expanses. The problem is, the father doesn't want her to do this.Every since they separated, he does thing s lie this just to upset my daughter. Sometimes he can be very spiteful. Legally, what rights do my daughter and granddaughter have? Can he actually stop her from vacationing with us? I'd appreciate any advice you could give me. Thank you, Pam Coms