You simply don't have the right to own/possess guns on probation... you probably were sentenced to x days in jail, with y days suspended plus z days on probation. until all x, y, and z have been completed, you are under the order of the court to do or not do certain things-- more or less-- at the courts discretion; these restrictions on your freedom can include owning/possesing guns.
Your father having the guns, assuming you don't live there, shouldn't be an issue and they never should have been seized in the first place... IMO, but, IANAL. I would suspect if you live there or have it as your listed address, that one of the conditions of your release is not being near guns (or at least not living in a house with them.)... but we would certainly need more details to really get to the bottom of this all.
What court was this in? Do you have the case number?