The legal heirs of your deceased father are his wife, children, the term children includes the legal heirs of the deceased children.
In this case the widow and the children of your deceased brother and the spouse as well as the children of your deceased sister (if she was married) form one of the legal heirs of per law.
Therefore considering it as intestate succession, the property can be legally divided into five equal shares if there is no consensus or amicable settlement ios arrived among the legal heirs/co-sharers to the property.
The legal heirs of your deceased father are his wife, children, the term children includes the legal heirs of the deceased children.
In this case the widow and the children of your deceased brother and the spouse as well as the children of your deceased sister (if she was married) form one of the legal heirs of per law.
Therefore considering it as intestate succession, the property can be legally divided into five equal shares if there is no consensus or amicable settlement ios arrived among the legal heirs/co-sharers to the property.
A Will whether registered or unregistered, is valid provided the same has been signed in all the pages by the testator before two witnesses who should attest the signature of the testator.
Your deceased sister forms one of the legal heirs to your deceased father, hence her share of property shall devolve equally among her own legal heirs which includes her husband and her children.
Therefore her husband is entitled to inherit her share in the property.