Father died intestate

YES, lot of times. your mother  and sister can issue RELEASE DEED OR RELINQUISHMENT DEED favg you,2, if your sister is alive her heirs cannot claim any share now 

Yes , your mother and your sister can transfer their share in favour of you by making release deed . When your sister is alive then no need to take noc from her legal heirs.

Agree with experts.

Your father's self acquired properties upon his intestate death will automatically devolve upon his legal heirs, in your case, it is your mother, sister and yourself.  If your mother would like to settle or execute a gift deed in respect of her undivided share in the property in your favor she can do so by executing an appropriate deed accordingly,it is a similar case with your sister too in respect of her share.  Your sister's child has no right or share in the said properties during her life time.  If your mother or sister want to relinquish their rights and execute a registered release deed in your favor they can do so, they do not  have to obtain anyone's permission for doing so.  Thus all of you three are entitled to 1/3rd share in the properties left behind by your father.

tell me to which community you belongs. i.e Hindu, Muslim etc.   If Hindu, whether you belongs to Mithakshara or Dayabhag School.  This information required to give correct opinion

Dear Sathish- Section 8 of the Hindu Succession Act, lays down the general rules of succession in the case of males. It states that the property of a male Hindu dying intestate shall devolve firstly, upon the heirs, being the relatives specified in class I of the Schedule. The Class I heirs include the Son, daughter, widow, mother and so on. As per the facts stated by you, your father died intestate.Yes your mother can trasfer her 1/3rd share to you for which your mother would like to settle or execute a gift deed in respect of her undivided share in the property in your favor.In your sister's case it is the same as your mother.After the gift deed is made by your sister and mother, they cannot further claim on their share. Your sister's son cannot claim a share in the said properties. You will be the owner of the entire property as your mother and sister have gifted their share to you. Rutumbhara www.lawkonect.com 09555 507 507