(1) In the above mentioned case, if your mother too had died then the property left by your father shall be divided into 3 shares, after paying due rights preceding inheritance. Out of the total the brother shall get 2 shares, while 1 share shall go to the sister.
(2) In case the sister on the request of the brother is ready to take the cash equal to her share instead of the share in the house and they fix some date for the payment (for example 5 years) with mutual understanding then it is right to proceed. It shall be enough to pay the settled price within the deadline and there is no need to pay extra amount.
Allah knows Best!
Darul Uloom Deoband