Can you tell me what kind of fungus is on my tree and how I can remove it?
This is a type of fungus that is an indicator of interior rot, and fungicides are not going to help. Ornamental fruit trees are not terribly long-lived and we'd guess yours are older.
Enjoy them for as long as they are pleasing to you and are not a hazard were they to fall.
You might consider having a certified arborist do an on-site evaluation on the overall health of the trees and give their opinion on your options.