Does G understand the damage they are doing or are they still in denial?
How much control does G’s wife have over the household finances?
G needs to want help. And an important means of helping is to prevent him having access to most of his cash. If he can be persuaded to sign over control over his bank accounts, or pay his pension into his wife’s account as soon as he receives it, and get a weekly allowance in return, that might help with the impulse control.
But he’d have to want the help. So the first step is getting him to admit that he has a problem.
It may also be worth the family consulting a solicitor. If he’s in danger of gambling away the house, there may be legal steps you can take. Including having the casino bar him (but this may depend on where you are, and how many casinos he has access to).