I think he became resentful of my having more success in life than he did. Growing up he felt superior because his family was better off than mine so he would always poke fun at be that if I don't make it I can live in his basement.
He had a cell phone when I did not, he always had disposable income. We were both fat.
As time went by he would always take shortcuts. While I worked hard and I became more successful he became more bitter and spoke less and less to me.
As I was working hard to lose weight he would be resentful that I am betraying my roots and I am trying to be just like the douchebags that were making fun of "us fat people". So while I went back to a normal weight he skyrocketed to almost double what he should be.
He married for the wrong reason because everyone was pressuring him to, he had a child because everyone was pressuring him and he is terribly unhappy.
He is stuck in his family business that he hates, whole I decided not to continue my father's business because it was not going anywhere and do my own thing. He would also poke at me that he won't betray his father that worked hard for that business.
In reality, I believe that he simply was too scared to branch out on his own and do anything, I don't blame him for that. What I do blame him for is lying to everyone that he is doing everything for noble reasons rather than admitting that it's cowardice, that he does not want to do anything out of his comfort zone so he makes mistake after mistake doing everything for the wrong reason.
Overall I think that this is a more common problem than people want to admit, people that hold you down are often the ones that are closest to you. They want to justify their failures on the environment thanks they grew up in, that "the game is rigged against you" so they justify their inaction based on that.
When they see someone that grew up in the same conditions as they did not you broke free of that environment, their belief that the game is rigged and that there's nothing that you can do about it gets challenged.
That conflict of emotions can be resolved one of two ways, either admit that you were wrong and that if you work hard enough you might just make it out. Or just believe that this was just luck or that the guy that made it out betrayed you in some way, that he sold his soul or some other bullshit to make you feel better about doing nothing to get out yourself and keep telling yourself that the game is rigged.