It might seem irrelevant to you, but one would hope that the other person had a good reason for entering someone who was a neighbour. For example, neighbours sometimes register a death - because they were the only person present at the time - or may work in the some trade. Or perhaps one of the children was living with, or employed by, the neighbour in a different census. These are just a few examples that spring to mind - you will only know when you ask.
However, if you discover that the other person didn't have a good reason you can suggest that they remove your relative(s) from their My Ancestors page. Once there are no shared entries you can ask me to delete the connection.