Yes, Husband can made Will in favour of his brother despite of wife survive.
Will is a legal declaration of the intention of a person with respect to his property, which he desires to take effect after his death. Will is an untitled document which state after the death of person making.
However, the validity of Will can be challenged by Wife or any other legal heir of the person.
There is no statutory time limit for claims to challenge a will however, in the event of inexcusable delay, a substantial lapse of time, or acceptance of benefit given under a Will, the court could conclude that the claim should not be allowed to proceed