bookmarks are double, even tripple

If I have too many bookmarks it is because they get duplicated and tripled  instead of just uploaded and then when I sync they get erased,  Luckily for me my household has more then one computer and I use them both. We have to share two computers between 3 people. So I went to the other computer and upload them to get back what I had lost,  but upload or download just duplicates. I miss xmarks that was a good program and it was free. Why would I pay for something when the free is so horrible.