To be type rated on an aircraft, you undergo a course of ground training in the operation of the systems of the aircraft which is completed by undergoing some form of written or computer set test. Then you undergo practical training in the handling of the aircraft in normal and abnormal situations - emergencies by flying the aircraft and/or it's simulator. Once this is satisfactorily completed the Civil Aviation Authority endorse the aircraft type on your licence. Any number of such aircraft can be endorsed, but the endorsement is only valid for 5 years unless the pilot actually flies the aircraft and undergoes recurrent training on it or its simulator.
Once the aircraft is so endorsed, the airline will further train and test the pilot to ensure their competency in operating the aircraft in accordance with the proceedures laid down by that airline (they are all different).
Hence your friend's uncle may have all those aircraft types endorsed on his licence, but before flying any of them for an airline he will have to undergo training to make him "current on type". With large airliners, due to their complexities pilots are rarely "current" on more than one type at a time. The one exception is the B757/767 which were specifically designed to enable pilots to be "dual rated" by making their handling characteristics similar and providing them with similar flight deck layouts.
P.P.