1. If your father has died without making any Will giving this proeprty to anyone,you have undivided 1/3rd share in it.
2.So you can very well claim your due share from your mother and brother who are in possession of the said proeprty.
3.if they refuse to part with your sahre you can file a suit for partition in the local court claiming your 1/3rd share.
4.In the same suit you can seek injunction order so in the meantime they may not sell the property to frustrate your claim.