Falcon Street, Pioneers Park in undivided shares

Mr. Jones bequeathed to his two sons and a daughter, Rose, his house No 20 Falcon Street, Pioneers Park in undivided shares. The two brothers live in Okakarara and Rose has been staying with her boyfriend John at the house in Pioneers Park.

The two brothers have recently discovered that their sister has sold the property for a paltry amount of $40.000.00 and caused it to be registered in his name.

The two brothers want to institute legal action for a declaration that the transaction is null and void on the ground that they have not given their permission and that they have irrefutable evidence that Rose was unduly influenced by John in her decision to sell the property.

They argue furthermore that Rose suffers from an impaired mental capacity induced by abuse of alcohol.
Advise the two brothers about their rights, if any, in the matter focusing on the following:
(i) the nature of their rights with regard to the property

and (ii) the validity of the transfer in the context of the abstract and causal theories of transfer.