I am pretty sure there was overlap with engines between Makon and Sachen, and then there was that one company that stole Vast Fame's rpg engine (I am pretty sure that Sintax version of Beggar Prince was by them). I think they were called Tian Cai Xiao Zi. There may have been some overlap between Hitek and Waixing based on what I have heard, but I don't know much about those two. Honestly, I think that making a family tree of all the unlicensed gameboy companies could make for a good poster
Edit: I must have been tired when writing this originally, there has never been evidence of Makon and Sintax being related to my knowledge