Dear Zanex,
That is terrible!! I am so very sorry. I have watched my husband go through simular attitudes with his parents as well. His only brother disowned him, and so has his grandmother, and by their actions his parents too. He has always been a hard worker and good provider, but his dad always makes comments like it was because of him. Or in essence that he was just lucky. He won't acknowledge, like your dad, all the blood, sweat and tears (not to mention plain old ass breaking work) he has endoured along the way, when his parents were no where to be found.
Hang in there!! We can relate, and understand a good measure of your sadness and frustration. Keep praying their hearts will soften. You never know!! There are many who are now out, that if you would have told them a few years ago this would be the case in the future, they would have thought you were crazy.
There is hope!! You never know what may happen in the future! Do you have other family, or loved ones that can fill that void in the meantime?? I really think that has helped my husband. Although it's not the same as your blood parents and siblings, sometimes its better!
Sincerely,
Lady Liberty