1. Well if the property has been registered in favour of all three of you then each one of you is a co-owner. The title to a property originates from its sale deed irrespective of who paid the sale consideration.
2. If, however, you have evidence to prove that entire sale consideration was paid by you then you may file a suit for declaration that you are the title holder of the property and the property is benami in the hands of your two brothers.