Dear Liz,

I had the same dilemma in trying to track down an older brother that I had found out about. I put messages on many genealogy websites and facebook over about 6 years only stating that the same person was in my family tree. Sometimes I tried the same person twice after some time. Last year a women replied to say yes that person was in her tree, but knew nothing about other relatives and wanted more information.
After many emails, all very discreet it turned out to be my brother. He did not know about me and my brothers and sister.
It all turned out great (bit like one of those shows on tv), but on the other hand it could have been a disaster because of the secrets families keep.
So keep trolling through all the websites and messages left by people and don't give up and be patient.
Cheers Diane