I think it depends upon the environment/upbringing of the person and his tenacity to play around with a highly speculative game. I've known some kids here in our country (Philippines) as young as 12-13 years old to gamble against adults, especially those who were born in the slum areas. They are usually children of gamblers as well, and they learn at an early age how to play against the psychology of an adult in a game in order to earn a bit of cash.
Well, that's illegal of course, and that's not a perfect age bracket for someone to gamble. For sure these kids are doing illegal stuff as well like stealing money from their parents or worse from another person.
I have seen children like these as well, and they are stubborn as hell. The least you can do is to report this to the authorities before anything worse will happen.
The sad thing is that their parents are perpetuating their own mistakes on their children, even if it is a bit hypocrite they should tell their kids to do as they say and not as they do, they should try to get them out of gambling but those parents that are addicted to gambling probably do not care anymore about what the kid does or does not do, and in some cases they could even encourage that behaviour as the kids end up bringing money with them and more than anything that is what those that are addicted to gambling want.