Delayed property registration- possibilities

Dear sir, my father purchased land in bangalore in year 1991 through GPA in my mothers name and failed to get it registered in the office but she passed away in 1995 before her death in 1992 she had given GPA in my fathers name in 2005 the seller son has generated 50% as a gift deed in his name. Tax and electricity bills are in my fathers name. now the actual thing is can my father register it to his name and get the full property rights to his name . please suggest me that what can my father do now. waiting for your opinions