"It was sold privately no agent or bank involved (from what I've been told) "
OK - point taken - it is a mess. BUT there has to be some paperwork and you have to ask the brother for back up. There has to be paperwork and if there isn't then yes, someone is lying somewhere. And, if you let him register the property in his sole name, is that not akin to giving it to him? Unless, of course, the house never was yours because your uncle died before transferring it to you in which case, it belongs to his estate and anyway would'nt there have to be a Grant of Probate anyway?
Get yourself a solicitor - even if you are still in the States - agree on and pay them a fixed sum up front, tell them the truth, the whole truth and nothing but and take their advices.
mf