NO, self acquired property of father and personal property of you and sister by registered release deed.

NO copacenars.

Is it personal property of all siblings on father intestate demise. And when release deed executed by brother, Sole ownership transferred in you and sister.

Since property is already transferred in your and sister name by brother in his life time. You both are sole owner and on sister`s intestate death, her share will inherit in you being class II heir. No claim of deceased brother`s legal heirs.

The property belonged to your father and after him to his children.

One of the siblings has died with no heirs and the other has given you his property. 

Therefore the property belongs to you now.

It is not a coparcenary property.

It is not ancestral property 

2) on sister death in 2010 property would devolve on you as her only surviving sibling 

3) your brother legal heirs have no share in property 

If it's self acquired it can't be coparcenary one. If it's not self acquired and turns to be ancestral then being woman she will be a coparcenary

1. Now it's a coparcenary property.

2. Before the amendment to Hindu Succession Act 2005, only son/s were coparceners. However in view of the amendment to Hindu Succession Act 2005, even daughters, whether they are married or not have become coparceners w.e.f. [deleted].

3. It's true that your Late brother had released his share in the property to you and to your unmarried sister through a registered Release Deed, but still his legal heirs will have equal share in the share of (your sister )who died intestate.

Even though your deceased brother had relinqushed his entitled share in the property in favour of you and your spinster sister in 1994, in view of your sister's intestate death in 2010, the family members of your deceased brother are entitled to equal share, totalling to one share in your late sister's entitlement.

It's not possible to take defense under 66B to your advantage against the legal heirs of your deceased brother.

ancestral property is a property acquired by your great grandfather.

It is not ancestral property. As per the law it is very clear that the property of a unmarried lady goes to the siblings.

1. No property is not coparcenary property. 

2. You all are legal heirs for property and not coparcenars because it is not HUF property.

3. If brother have excuted release deed in your favour then his legal heirs cannot claim the property unless they can prove that deed was obtained by some fraud.

1.  No, this is not ancestral property having any coparcenary rights, this was your father's own and absolute property.

2. No, all are legal heirs/successors in interest to succeed to the estate that belonged to your deceased father who is reported to died intestate.

3. Once your deceased brother had relinquished his rights in the property by executing a registered release deed in favor of other cosharers, nobody other than the cosharers have rights in his share of property.

On father demise his share in property would devolve on you and deceased brother share in property on his widow and son 

2) I presume your mother predeceased your father 

3) if registered release deed has been executed Widow and her son would have no share in property 

If your sister died intestate then the properties lying on her name shall devolve on her  legal heirs, in the following order:

The property of a Hindu female dying intestate, or without a will, shall devolve in the following order:

1. upon the sons and daughters (including the children of any pre-deceased son or daughter) and the husband,
2. upon the heirs of the husband.
3. upon the father and mother
4. upon the heirs of the father, and
5. upon the heirs of the mother.

Your question: that you being the legal heir of your deceased father and the widow  as well as the son of your deceased brother also being legal heirs of your father, can very well inherit the properties lying on your sister's name.

2.  The second question  may not be maintainable because the question of estoppel do not arise.

The property belongs to you as the brother has signed a release deed.

If sister is married then you will be class 2 heir. Only in property given by your father to sister before marriage you will become class 1 heir and your sisters husband side will be class 2

Dear Sir,

Your question needs deep study and to some extent it is correct that you are class 2 heir as such the matter needs to be studied in the background of all other factors and it cannot be answered in a straight manner without looking into history of your family.

Yes,

No estoppel here.