You should be able to fix this using the EDIT tab at the top of the profiles.
While in EDIT - On the right hand side you will see father/mother/children etc. with add/edit underneath. Click the add/edit button on the person you wish to remove. On the next page choose the Remove button.
Once that is done, you can go back in and while in EDIT again, you can place them in the correct relationships by using add.