Why there are different spellings of similar last names.
Names change over time.
Ask your parents or grandparents if your name has changed over time in the way it has been spelled. One man's name was Salaman when his ancestor emigrated to America in the late 1800s, but his ancestor decided to change it to Sullivan. Sometimes spelling was changed to suit the English alphabet and its language of spelling and pronunciation. Sometimes other people didn't like someone's name. Many Schmidts became Smiths.