Can my grandfather become an american citizen if his dad was an american citizen?

So here is the story. My great grandfather was from scotland and he moved to Mexico, and he secretly had two girlfriends at the same time, my great grandmother and another woman, he first impregnated my great grandmother and a few months later he impregnated the other woman. He decided to marry the other woman, and when my grandfather was born he didn't even recognize him, so my great grandmother decided that if she couldn't get my great grandfather's love she would abandon him and so she did. My grandfather grew up alone with no family, in a very poor mexican town, eating roots of the trees to survive, while my great grandfather was a very rich man, he had mines throughout mexico and a lot of ranches with livestock, he was among the richest men in Mexico. He then invested in the US, and he obtained the citizenship for him, his wife and his 4 children. Many years later in life, when my great grandfather was 90 years old, he decided to recognize my grandpa, two months later he died. My grandfather siblings all live in the US because they are American, but my grandpa isn't, and he wants to be an American citizen so badly. Is there any way? By the way my great grandfather had a lot of properties in the US, and some of them were meant to be for my grandpa, but his half siblings took what belonged to my grandpa and never told him, how can he claim those properties?