Hindu succession act?

We are 3 brothers , one married sister and mother. My father died 15 years back. Family was having
one shop which was purchased by my father and made my mother 50% share holder in order to save tax. At the time of purchase my father was the only earning member of family and first installment was made from the income of business of which he was propritor.
One house which was purchases by my father in the name of my parental grand mother. The house was gifted by her to my mother.
Father left an unregistered will giving his 50% share of shop to 3 sons only. We all 5 applied for transfer of 50% share among 3 sons on basis of will.But estate office did not accepted the will as signature did not tally. so the 50% share was divide in 5 parts (3 sons, mother, 1 daughter).
Also as per will mother is given owner ship of business which was run by my father.
Now 2 brothers & mother have jointly put a court case against me to partition the property.
Kindly write how can I protect myself.

I would go away and start a business on my own. This situation doesn't sound happy now or in the long run. It is bad for business and I can't see success in this energy.
Perhaps it is a sign that your destiny lies in other direction.
I wouldn't fight it. Bless them all and leave.

You all 3 brothers, your sister and your mother have equal right in the 50% share in the shop which your father was having. The law says so in case of lack of any legitimate will.
It is advisable to settle the matter amicably instead of spending time and money in the court.