this subject is close to my heart!
A story I have told before and am happy to share again ....
My ggrandfather Mordechai KASSEMOFF was born in Rezekne in Latvia. On his papers that I had received from the Latvian archives, it said that his father was Moshe Hirsch. However, on his tombstone, in Leeds, it said his father was Zeev.
During my years of research I came across two family ancestors - GREENSTONE/GREENSPAN and MULVIDSON, and I couldnt understand how they were connected to the KASSEMOFFS. Eventually I was in contact with a descendant of one of the MULVIDSON family, who lives in Norway, and he sent me a copy of a photo taken in 1926. He told me that on the reverse side of the photo was written: my brother Mordechai and family in Leeds. Imagine my shock when I received the photo (attached). I had the identical photo in the cupboard of my ggrandfather and ggrandmother and their grown children (including my grandparents). He told me that the original family name was MULVIDSON. Ggrandfather Mordechai's birth father was Zeev. The clue of his birth father was on his tombstone . The GREENSTONE/GREENSPAN (I have found different surname information and spellings, for the same branch) is the 2nd brother. There may have been more but because of the different family surnames, it's not easy to find them.
I was told that they had been given different surnames almost at birth, to avoid conscription. The oldest son kept the family surname as he was exempt from army service.
Hope this has helped.