Hi 

Since your grand father has done his second marriage after the demise of his first wife, the 2nd grand mother is a legally wedded wife and she is entitled to a share of her husband's properties.

The properties of your grand father will vest on his legal heirs in accordance with Section 8 of Hindu Succession act (assuming your grand father had acquired these properties out of his own income).

The legacy will be governed by Schedule I of Hindu Succession Act wherein the class I heirs would be 

a) Your father

b) Your uncle 

c) Your 2nd  grand mother and 

d) Any children born out of wedlock from your grand father and 2nd Grand mother. 

However your 2nd grand mother cannot claim any share that is devolved on your father as she is not a biological mother to your father. 

Hope this information is useful.

She is your father step mother 

she has no share in deceased father property 

On grand father demise property standing in his name would devolve on his second wife , 2 sons from first marriage and children from second wife 

On her demise property would devolve on her children 

Property standing in her name would devolve on her biological children only 

Your grandfather's second wife is just a step mother to your deceased father hence she cannot become a legal heir to him. 

Therefore she do not have any rights in the share of property pertaining to your deceased father. 

Your step grandmother is also one of the legal heirs to your grandfather hence her share in the property shall devolve on her own children and not on the children of your deceased grandfather's children of first wife. 

Hi 

1) The property of your 2nd grand mother will be inherited by her biological children only. 

2) Yes, since your father is not alive, you can claim your father's share. 

Hope this information is useful. 

Since your deceased father was one of the legal heirs of your deceased grandfather,  he is entitled to an equal share in the properties left behind by your deceased grandfather. 

Being the legal heirs of your deceased father,  you can claim his share of property by a partition. 

If the others do not respond for an amicable partition you can file a suit for partition and claim your legitimate share with separate possession. 

1. The share of your step grandmother shall devolve equally only on her own biological children. 

2. The legal heirs of your deceased father can claim his legitimate share in the property. 

When a Hindu male dies intestate (without leaving a will), his property devolves upon the legal heirs as per Section 8 of the Hindu Succession Act, 1956.The heirs of Hindu male fall under the following categories:-

1) Class I heirs,

2) Class II heirs,

3) Agnates,

4) Cognates, and

5) Government.

Class I heirs:-

The property of a Hindu Male dying intestate would be given first to heirs within Class I. They are:

1. Mother,
2. Widow,

iii. Daughter,

1. Son,
2. Widow of a predeceased son,
3. Son of a predeceased son,

vii. Daughter of a predeceased son,

viii. Widow of a predeceased son of a predeceased son,

1. Daughter of a predeceased son of a predeceased son,
2. Son of a predeceased son of a predeceased son,
3. Daughter of a predeceased daughter, and

xii. Son of a predeceased daughter.

Son in Your case ,

The second grand mother has right over her husband’s property. But she has no right over your father’s property. After the demise of your father,. your father's shares (He obtained by way of succession (he is entitled to an equal share in the properties left behind by your deceased grandfather) and the owned properties by his income divided among his class I legal hairs only.  

In the second grandmothers property, the share shall devolve equally only on her own biological children. 

Inform tehsildar that she is your father stepmother and not biological mother 

2) rely upon birth certificate of your father to prove that step mother is not biological mother of father 

- No, she cannot claim any share in the property left by your father . 

- After death of your father , his property would be devolved upon his legal heirs equally only , and the 2nd grand mother was not his legal heir.

- Further, being the legal heir of your father , you can claim over the property left by your grandfather legally, including the children of 2nd grandmother. 

1. Apply for getting legal heirs certificate of your father , after submitting his death certificate and name of all your family members, and submit the same before the Birth & Death Registrar for correction .

2. As above.

You need to get legal heirship certificate from court in the said case

1. You may have to produce the birth certificate of your father in which his original or biological mother's name is found and the documents to prove that she was your father's first wife. His educational certificate containing his biological mother's name may also be produced to establish this. 

2. With the help of documentary evidences. 

Dear sir/ma'am,

The grandmother can only enjoy the rights of the property and  can claim the right to live in it etc. she can not sell the property, she will have the share till she is alive.  the property will be transferred to the sons and daughters of the grandfather equally.