Can not add profile for father

I'm  trying to add a profile for father of someone in tree, however it seems that this profile is already managed by someone else.  My problem is, they have father added as UNKNOWN, I'm presuming, to manage profile of  someone they have no knowledge of at this point, & block anyone else from doing this, even though they have no knowledge of this person's identity.  Is that even ok to do?  I mean, should I, even though my tree stops at some point because I don't know who should be there, tie up a infinite number of profiles & name them all UNKNOWN so that I & I alone will for all times own management of these profiles?  Please advise