Find Ancestors

Not Brown Really but a spurios link. I am actually trying to trace a man who may have been involved with Marie Gertrude Brown in the 1920's. She was the only Marie Gertreude Brown born in England in 1897 in Brighton. During the 1920's she got involved with a married man from maybe Sussex or Surrey and his name may have been Gardiner. My father-in-law was the result of this union and although he passed away in 1992 he died not knowing who his father was and his mother never said. There was talk passed down the family that the married man and his wife stayed in regular contact with Marie so it was all amicable. Marie moved to Surrey around the 1930s and the other couple still stayed in contact and regularly dropped off money. This is where I need help. Not many familes spoke of such things but maybe down some family line there is a tale of such an event. I have a photo of the man. If anyone wants to see if they can put a name to it I will email them a copy. This is a desperate act I know but I really have no other way of finding out my father in laws roots. Many thanx