If you Google genetics and OCD you will find tons of info but check this out

"Incidence and Prevalence
The National Institute for Mental Health reports that about 3% of people in the United States have OCD. Typical age of onset for boys is 6 to 15, while for women it is often later, between 20 and 30. Risk factors like genetic predisposition and environmental stress contribute to OCD. Also, OCD is more common among people of higher education, IQ, and socioeconomic status. Men and women, however, are affected equally. Though its course is chronic and usually lasts a lifetime, it is treatable with medication, behavioral therapy, and, in extremely rare cases, brain surgery.

Risk Factors

Risk factors for obsessive-compulsive disorder include the following:

Genetics
Postpartum periods
Environmental stressors
Although there is no clear genetic evidence, obsessive-compulsive disorder tends to run in families. A person with OCD has a 25% chance of having a blood relative who has it. Like other mental illnesses, it is more prevalent among identical twins than fraternal. There is a 70% chance that identical twins with share it, and a 50% chance for fraternal twins. Currently, researchers do not understand OCD’s genetic mechanisms, though they suspect multiple genes are involved. "