Yes. But it is very difficult to prove. If you kept a good log of whom you talked to, and when, where, and what you showed them, you may be successful. For example, if you had an idea to make a singing pen, and you tell your sister your idea and she actually manufactures the pen before you get a chance to manufacture it, the mere fact that you thought of a product and your sister manufactured it before you did does not make your sister liable to you. However, if you drew up the plans for the design of the pen, showed the designs to your sister and she actually used your design to manufacture your singing pen, she will be liable to you.