It is presumptively your money to keep. Unless sister could prove that it was intended only to have you on there for convenience, to pay bills and such, it is yours. Since it is likely impossible for her to prove this I would say it is yours to keep legally speaking. If you want to give her 1/2 you can but I do not see a legal obligation to do so.
Answered on Dec 02nd, 2014 at 7:14 AM