Rights of Residence are common in wills, particularly around farms etc
Simply put, your brother has to accept that you have a legal entitlement to live there.
Your brother might attack the will on the basis that your Dad did not make adequate provision for him, and that the house should be sold. Whether such an action would be successful would depend on the facts and circumstances of the case.
Depending on the wording of the will, it might be possible for the Executor to sell the house, but with the Rights of Residence being incorporated into the sale. I have seen cases of such sales. Obviously, the value of the property would be greatly reduced by the Rights of Residence. The purchaser would have to wait until the last of you and your siblings passed away before he could get vacant possession.
The Executor could attempt to "buy out" the Rights of Residence, but he would have to buy out all 3 Rights.
Jim Stafford