About Inheritance Gift From Mother
If your father gave 20 marla land to your mother at the time of nikah as mehr (dower), then that 20 marla legally and Islamically belongs to your mother. It is her full property. It does not belong to the children and it is not part of your father’s inheritance.If that is the case, then your mother has full right to give her own property to anyone she wants — to sons, daughters, or even charity. It is not a sin for her to gift her own land. The remaining 36 marla is inheritance. That must be divided according to Islamic inheritance law among all heirs: mother and all five siblings. That part cannot be changed based on personal wishes.