Nomination to the society enables only transfer of membership of your late father. to your mother. Get it done first, since, in any sale transaction, your mother as ther senior legal heir of your father has to sign, the deed, and purchaser would insist on the membership of the society in her name,at least. Also, payment of maintenance charges by her will be with proper proof of receipt by the society in her name.
In the absence of a will, all the class 1, legal heirs would succeed to the property. In your case, it would be your father's mother (if alive), your mother, you, your major sibling and two minor siblings.
As per law, minor's interest in property can not be alienated by the guardian (your mother), without the permission of the court. But many people do, mentioning clearly the purpose of sale, as for legal necessities for rearing, maintaining, food, medical and educational needs of the minors, and mostly purchasers do not insist on court order. But some purchasers who are extra precautious, insist.
Try for sale without court procedure, which may entail enormous time lag.