If the property is devolving around 4 generations without partition then only it is coparcenary property. Otherwise it will lose its character of the same

1. You see, after partition, your​father's share became definite and it no longer remained a coparceneray property. So your father is well within his rights to Will it as he pleases. 
2. So the suit filed against you guys will not stand judicial scrutiny. Of course you guys need to appoint competent Advocate to defend your interests. I'm willing to offer my services in this regard, but for that I require an exhaustive consultation session with you first. So do pay me a visit.

1. At present the property belongs to your father. The Will will operate only after his demise. So o fail to understand why have you been made a party to the suit?

1) it is not ancestral proeprty

2) property which has remained undivided for 4 generations is ancestral property 

3) once partition deed was executed between father and his siblings it would be father absolute property 

4) he could execute will in your favour 

5) sisters have no share in property 

Let them file a suit in this case as they need the share you only contest the same. It can turn in your favour

This is not an ancestral property. Property needs Tobe four generation old to become ancestral that is to be passed down from great grand father to great grand son.

Will made by your father shall be valid. You shall have full right to the property. Your sister shall not have any right.

No it is partitioned and as good as self acquired property father can dispose same in his will.

File application before court for rejection of the suit.

1. the property was purchased by your GF in 1939 i.e. prior to coming into force of the Hindu Succession Act

2. so the property is indeed an ancestral property or HUF property

3. the Hindu Succession Act was amended in 2005 by which even daughters were made coparcenors in ancestral property with the condition that the father has to be alive on the amendment date

4. your father is still living which means your sisters automatically became coparcenors and thus have a legal share in this property

5. your father can make a Will of only his undivided share in the ancestral property and not the entire property - see section 30 of Hindu Succession Act

NO, and in father life time,non have claim in property. Ask your father to gift the property.

After partition, the property in the hands of the son will continue to be the ancestral property and the natural or adopted children of that son will take interest in it and is entitled to it by survivor ship. It is a coparcenary property if 4th generation born.

According to the law, all coparceners acquire a right over the coparcenary property by birth, while their share in the property. 

This is not ancestral property. 

This becomes your father's own and absolute proeprty hence ther is no coparcenary rights in it to anyone.

Your father is competent enough to dispose his share of property to anyone of his choice and decision.

His decision cannot be challenged by anyone.

Hence your sisters partition suit may not be maintainable.

You contest the case properly and challenge their claim as per law and repudiate their claim.

Their case is not maintainable or tenable in law.