Well, like I mentioned before, I personally don`t think Pumbaas family abandoned him. I believe Pumbaa simply left when he became old enough to take care of himself. Then, when he tried to get his own territory/make a home for himself in a different area, the animals couldn`t stand to be around him because of his stench.. so they drove him out. After that, he wandered aimlessly as an outcast, not being able to settle anywhere because none of the other animals could handle the smell. Then, he met Timon.
I just dislike the thought of Pumbaas family being so cold to someone of their own kind. They`re all warthogs, so I reckon they all have problems with various odours.