Pro users can disconnect any connection on their tree,
Non-Pro users can disconnect only link that doesn't cut the profile from the tree.
enter to the "edit profile" and then to "Relationships"
you will see an option to remove connections.
Private User and Yaacov Glezer At first you shall make correct link between 2 correct persons.
After creating such "loop" even non-PRO can cut wrong connection (as the correct one keeps remaining tree in one piece).