Your brother should be aware that most Wills are adhered to, the courts will not alter the terms of a will just because your brother asks them to.
The claim process can be very expensive and take a long time. Realistically unless your brother was financially dependant on the testator at the time of the death there is little chance of his claim being successful.
That is assuming he is contesting under the Inheritance (Provision for Family and Dependants) Act 1975.
If he is challenging the Will because he believes the testator was not of sound mind when the Will was made, or there was coercion or undue influence, or a clerical error in the Will, or he was relying on a promise the testator made, or that the testator was not of sound mind when he made the Will that is an entirely different matter.