Being born dead and dumb is truly one of the worst faiths that can be dealt on a person, and it's not something that anyone can handle easily.
As far as deafness goes it could possibly be caused by genetic reasons. Its possible that deafness may run in a person's family and whether or not a child will inherit the deafness gene is unpredictable. That isn't the only reason why a child could be born deaf, certain drugs which are commonly known as ototoxins could damage a child's hearing before they are born. Certain illnesses during pregnancy could also cause the child to become deaf, illnesses like rubella, cytomegalovirus, toxoplasmosis and even herpes could end up making a child deaf.
Children that are born deaf often become dumb as well, that's why they are referred to as dead and dumb. The children become dumb because seeing as they can't hear, they aren't able to understand and properly assimilate languages and as such they become unable to speak, not because they can't but because they don't understand the concept of spoken language it self.
Being deaf and being born dumb are almost always mutually exclusive and children that are born this way often experience rather difficult lives.
I hope this helps.
Sometimes that is just the cards you are dealt.