Is Homosexuality hereditary ...??

So many times I asked this to myself and my friends ... The response that varies from person to person, but it seems that is scientifically proven that homosexuality is not hereditary. However, speaking in my personal experience, I have some doubts that it is ... This is because in my family there are three known cases, and another suspect if not given. By coincidence or not, everyone is the same side of the family ... Will not match the most?