Is paget's disease genetic?

Sometimes. There are two diseases termed "paget's disease." one is a rare type of breast cancer with unknown, likely multifactorial, etiology. The other is paget's disease of the bone for which there is a genetic predisposition and exposure to certain viruses may trigger the disease. Here's a link to more info about pagets of the bone: http://www.Mayoclinic.Com/health/pagets-disease-of-bone/ds00485.
It can be. There is a genetic variety and some believe it may also be virally induced.