1. iIt is not clear how your mother became owner of the properties which your uncle seems to have illegally transferred the same.
2. However if your mother was owner of few properties which she left at the time of death, you and your sister became its joint inheritor.
3. Now if your uncle became your guardian then he cannot sell the same without taking permission of the court as long as you remain minor.
4. Now on attaining majority you can file suit for setting aside the same.
5. So take information of those transfers and file a suit accordingly.