Hi David, you don't mention if the child has been added to the wrong parents or if they are living and have been added by mistake.
In the first instance you can disconnect the current parents on the edit page and then join the child to the correct parents by using their wiki ID.
If it is something like the second scenario the best option is to use the profile for another family member with the same surname by again disconnecting and associating with a different set of parents.
HTH