A gambling addict always think he would make it through gambling despite his or her loses, the idea is that one day will be their day. so to help such people as a member I think is to draw them closer show them some love so they will have interest to what ever ought to say to them. let them know that it's not as they think, give them a constructive reason why they have to leave it because gambling is a thing of 50/50 chance. many people are in mess today because of gambling
Even if he lose, he will hard to pass the gambling because he wants to retur to the gambling to recover his losses. Other family members need to get closer to that gambling addict and try to show their good intention to help the addict. If the addict can see that their family member really wants to help the addicts, he will try to open himself and grab their hands. Together, they will try to solve his gambling addiction without hesitant because they are one big family that want to help each other.
If his family members can show their empathy to the addict, he will want to listen what his family members tell and follow it because that gives a good for him. Yes, it needs patience to help the addict to solve his problem but it's worth doing that as the addict will see how strong their bonds and not thinking about what he already did because his family wants to help him to solve his gambling addiction.