There is more physical evidence that he was born in Kenya then the adoption in Indonesia.
Video of his grandma stating she was present
Article in Kenyan newspaper in 2004 states he was born in Kenya.
Statement in Kenyan parliament transcript that he was born in Kenya.
True, but you have to weigh all of the evidence and come to a conclusion. I just haven't seen anything that leads me to believe that a massively pregnant teenager would, in 1961, travel all the way to Kenya to deliver a child when it seems likely that the only real role of the father in all of this was the impregnation event. I could be wrong, of course.
The testimony of his family and representations of the Kenyan Parliament do have be taken with a grain of salt.