How to tame a 15yr old possibly cage bound atiel?

about two months ago i acquired a 15 yr old atiel from my mom, and she was afraid of him because he bites so he hasn't been handled in a very long time. I've been around the bird his whole life but i wasn't allowed to handle him because my mom was afraid of him biting me. he will talk to me and whistle, but if i try to put my hand in his cage he hisses and spreads his wings and tries to bite i know this is because he has almost never been handled, but i was wondering if there is anything i can do to tame him, I've tried to get him to eat out of my hand with no luck, and i talk to him for at least 20 min a day if not more, is there any hope for my poor birdie?