As it stands now:
(a) your brothers are losing out financially (even if they're happy to do so) because they're not receiving the rent that they could charge if someone else was living it the house ; and
(b) you're left with the uncertainty as to whether it's worth spending any great amount of money on the house (remembering that, if one of your brothers was to find himself in financial difficulties, he could seek an order to enforce the sale of the house).
As I see it, it would make more sense for you to seek to buy your brothers' shares in the house now, putting money into their pockets and removing the uncertainties you're currently facing.