Only if you say so. When you swap someone, we show you everyone who got their surname through that person's line, generation by generation, and ask about each one: change it, keep it, or not sure yet. There are also buttons to change all or keep all in one go. For example, if your great-uncle should really be a man with a different surname, you'll see his children and grandchildren who have his surname and can choose for each. Anyone who married into the family, or already has a previous surname, is left alone.
Still stuck? Talk to a real person: send us a message, or email support@mywholefamilytree.com