Partition deed -challenge

We are a Hindu joint family. we are two sons and one daughter for my father. Among us we had one Un-Registered partition ten years back (from the joint family ancestral assets) signed by my father and myself and my Bro & sister and each one alloted one schedule ( not equal share to all > due to verbal assurance of my father that he will do settlement deeds after wards ) Subsequently after one year

Due to misunderstanding between my father and my Bro. my father executed one settlement deed in my favour & my Sister( from the schedule of assets he got from the above said partition ) Father expired 5 years back.
Now my Bro is going to challenge the said partition saying that it is unfair and not equal & he does't know the settlement deed executed by my father 
Can he do so ? If so on what grounds ?
Kindly reply with expert answer so as to proceed further in my side if my Bro. challenge the partition