I have a second cousin who is a celebrity and is married to another celebrity. He wasn't in constant contact with my family, but when a relative passed away, I know my family contacted him because he was in a will. I believe they contacted him thru an agent. Your best bet is to provide some info to the agent. If they knew your father, maybe say its in regards to..
Give them the opportunity to make first contact, then let things play out. Personally I wouldn't rush things about trying to make friends. If its meant to be, it will happen.