Can Co-Owner sell a jointly owned property.

We have given some money to buy a property to my maternal uncle after taking money he bought a property (House) with joint ownership on (Maternal Aunt/ My Mother's) name. But he never handed a copy of sale deed to us. After few months due to some family issue our relationship become displeasing. He (powerful man) then told to us that he never bought any property on her's sister name (my mother) and denied to pay the money which we have given to him to buy property. We had given money to him in cash so we were not having any proof because of that we were not able to lodge any complain against him. After 18 Years I've found through official government website (Land Registration Department) that he had actually bought the property on (Maternal Aunt/ My Mother's) name. But the current situation is one of the CO-Owner i.e. my mother passed away few years back. I wanted to know; Who will be the successor of the Co-Owner i.e. my mother ? If me or my father will be the inherit. So can a Co-Owner sell/transfer his portion without the consent of other Co-Owner ?