On my dad's side, who are of Jewish decent from Russia, going back about 5 generations my great(5th)grandfather had 10 kids with his wife. It was customary in those days for a women's sister to take care of the kids should she die. But her sister was a widower herself and had 11 kids. Well they married and then they had 8 kids, so there were 29 kids altogether. Who could afford that???? About 35 years ago a family tree was developed and found over 2000 family members all over the world that are decendents from these 29 kids. Some of them died young from illness and others during wars, but most of those that survived moved out of Russia. Some went to Israel which back then I think was Persia (correct me if I'm wrong), some went to Spain and others traveled to America. Before arriving at Ellis Island they were told they were going to be asked 3 questions. What is your last name, what is the town you are from and how old are you? Noone could speak English. One group of family members that came over when they got off the boat, they were split into groups. The person asking the questions in one of the groups reversed the first two questions, so we had the same family with a different last name documented. When it was found that a mistake was made, they were told it couldn't be changed. So some brothers (and sisters) had different last names.
On my mother's side, years later, same thing happened to her father and uncle. They came from Austria. The Uncle acually came over on an earlier boat and by the time it arrived at Ellis Island, my grandfather was on his way so there was no way to contact him. They switched the questions again so when my grandfather came over, he couldn't find his brother. They searched for months for each other and finally found a mutual friend. By that time, you could change your name, so my grandfather changed his last name to the same as his brother. It's ironic that 100 years later between my father's ancestors coming to America and then my grandfather in the early 1900's the same problem arose.