daughters would have equal share in property 

2) on demise of son his his one sixth share would devolve on his son and daughter 

3) on demise of daughter her one sixth share would devolve on her children 

Dear Sir,

After the death of your  grand father it naturally devolves on the following formula

Section 8 in The Hindu Succession Act, 1956

1. General rules of succession in the case of males.—The property of a male Hindu dying intestate shall devolve according to the provisions of this Chapter—

(a) firstly, upon the heirs, being the relatives specified in class I of the Schedule;

(b) secondly, if there is no heir of class I, then upon the heirs, being the relatives specified in class II of the Schedule;

(c) thirdly, if there is no heir of any of the two classes, then upon the agnates of the deceased; and

(d) lastly, if there is no agnate, then upon the cognates of the deceased.

Hindu Succession Act, 1956 [Section 8]

HEIRS IN CLASS I AND CLASS II

CLASS I

Son; daughter; widow; mother; son of a pre-deceased son; daughter of a pre-deceased son; son of a pre-deceased daughter; daughter of a pre-deceased daughter; widow of a pre-deceased son; son of a pre-deceased son of a pre-deceased son; daughter of a pre-deceased son of a pre-deceased son; widow of a pre-deceased son of a pre-deceased son.

CLASS II

1. Father.
2. (1) Son’s daughter’s son, (2) son’s daughter’s daughter, (3) brother, (4) sister.

III. (1) Daughter’s son’s son, (2) daughter’s son’s daughter, (3) daughter’s son, (4) daughter’s daughter’s daughter.

1. (1) Brother’s son, (2) sister’s son, (3) brother’s daughter, (4) sister’s daughter.
2. Father’s father; father’s mother.

VI.. Father’s widow; brother’s widow.

VII. Father’s brother; father’s sister.

VIII. Mother’s father; mother’s mother.

1. Mother’s brother; mother’s sister.

Explanation : In this Schedule, references to a brother or sister do not include references to a brother or sister by uterine blood

If the grand parents died intestate, all have 1/6th share each and deceased sibling share will inherit in their legal heirs.

But in this case due to great G children - so in each 1/6th share, GGC of each sibling also have share.

The property will be distributed among all sibling whether daughter or son.

The property will be distributed in 6 equal parts for 3 sons and 3 daughters. 

The share of deceased son and daughter will be equally distributed among their children. Which will be 1/12 for son and 1/12 for daughter. 

1/6 for son1

1/6 for son2

1/12 for son3's son and 1/12 for son3's daughter

1/6 for Daughter 1

1/6 for daughter 2

1/12 for daughter3's son and 1/12 for daughter3's daughter

All the sons and daughter will have equal share of the said property. For instance total legal heirs 4 then 1/4th each. If the legal heirs are dead then their heirs will share the share in equal proportion as per the numbers

Each sons and daughters shall have equal right to the property. Each will get 1 share in the property. Surviving sons and daughters of each deceased son or daughter shall take between them one share. 

1. Since the property gifted to your grand father by his wife is not his ancestral property, it is liable for division among his sons and daughters in equal share,

2. So each son and daughter has undivided 1/6th share in the property and their children have no share in it.

3. Any son or daughter having died in the meantime, his 1/6th share would be further divided among his living chlldren. 

1. It's not clear in your question as to whether your grandparents died intestate (without executing a WILL) or had they died leaving behind a WILL.

2. In case they had executed a WILL, then the entitlement to the property would pass on to the beneficiaries as detailed in the WILL.

3.  In case your grandparents had died intestate, then share  in the property would devolve equally to all their children, in the instant case to their 6 children. Daughters' are also entitled to equal share on par with sons.

4.  In other words,  each legal heir is entitled to 1/6th share in the property. In case of deceased legal heirs, the entitled 1/6th share will be further subdivided amongst his /her children totalling to 1/6th share.

5.  In the instant case, 1st son, 2nd son, 1st daughter and 2nd daughter are entitled to a share of 16.66% (approximately). The deceased 3rd son's son(grandson) is entitled to 8.33% (approximately), alongwith his sister who is entitled to 8.33% (approximately), totalling to 16.66% of their deceased father's share.  Similarly, the deceased 3rd daughter's son (grandson) is entitled to a share of 8.33% (approximately), alongwith with his sister, who is entitled to 8.33% (approximately), totalling to 16.66% of their deceased mother's share.

Any property at the point of its partition is divided among the legal Heirs equally at the first stage and later on if the legal hairs property is again partition it will be decided based on the legal hairs at II stage and so on.

Daughters will have the equal rights in ancestral property along with their other siblings and increase any legal hair has been expired his legal Heirs will definitely get there shares in the property

The property can be amicably divided by making a deed of partition among all the legal heirs 

all legal heirs get 1/6 share 

deceased son and daughter legal heirs can claim equal share. 

The provisions of hindu succession act 1956 provide for succession among Hindus 

According to the Hindu Succession Act, 1956, a son or a daughter has the first right as the Class I heirs over the self-acquired property of his or her parents if they dieintestate

Hindu Succession (Amendment) Act 2005 gives equal right to daughter in ancestral property. 

As per hindu succession amendment act 2005 both father and daughter have to be alive on date of amendment of hindu succession act for daughter to claim share in ancestral property 

2) property which has remained undivided for four generations is ancestral property 

3) you have not mentioned details of suit filed in which court decree has been passed 

2005 amendment is related to birth right of great grand daughter in ancestral property, earlier it bestowed to great grand son only.  Since 1954 daughter being class I legal heir have equal right in parents property.

Check class I legal heirs schedule.

Recent judgement of supreme court has clarified the same as daughters have right by birth

https://www.google.com/amp/s/www.indiatoday.in/amp/education-today/gk-current-affairs/story/supreme-court-clears-that-women-born-before-hindu-succession-act-2005-also-have-ancestral-rights-[deleted]

Supreme Court latest judgement made it clear that a daughter living or dead on the date of amendment of the act will be entitled to equal share in father's property, thus her children too to claim this right.

Your brother is right. But that law will not be applicable to your case as it seems from the facts mentioned in the question.

Take note that if you be a great grand child in relation to great grand father only then the property becomes ancestral and the conference right of daughter shall be applicable.

In other cases father's property shall devolve upon all legal heirs including daughters equally as per intestate succession law give in the Hindu succession act. 

Subsequent to the Amendment to Hindu Succession Act in 2005, there are many SC Judgements, which have ruled that irrespective of the date of father's death, still the daughters are entitled to equal share alongwith their brothers.

The property that belonged to your great grand mother is not an ancestral property, in fact after the same was transferred to your grandfather by a registered document, it becomes your grandfather's own  and absolute property.

Now upon his intestate death the same shall devolve equally on all his own legal heirs, i.e., his six children.

The share of property pertaining to his deceased legal heirs shall devolve equally on their own legal heirs.

However the property that is on your grandfather's name shall be divided into six equal shares and the respective legal heirs can avail one such share equally or can arrive at an amicable partition as per the conditions and terms mutually agreed among themselves,.

The Hindu succession Act with respect to intestate succession makes the provision very clearly which would enable the daughters to have equal rights on their parents properties at par with their male counter parts i.e., the sons.

In case of any doubt in this regard you may consult a local advocate and proceed.

Your brother is not the law maker nor he is an authority for Hindu law.

The Hindu succession act 1956 is clear about this provision enabling the daughters having equal rights in their prents properties at par with the sons.

You were advised to consult a lawyer in the local and file a parition suit to claim your legitimate 1/6th share in the property with separate possession.

The amendment of 2005 is applicable on the property of Hindu Undivided family and not on individual property