An American decided that my grand-parents were part of his ancestry, apparently my gran had dozens of children, all over Europe and America, sometimes several in a year, spanning several continents, she was also married many times. Her sons were born and died in America and one died in Sulewasi during the 2ww. None of this is true, they were all English and the one that died is honoured in Portsmouth.
The problem is that people copy other trees without doing their own research, it's hard work but you get the correct results if you diy. Even distant members of families make mistakes, the amount of times I thought I'd found the correct family and realised that I'd been on the wrong trail, I wish they hadn't used the same names over and over again!