Now that's a very hard question. If I allow it, it means I'm also giving him permission to gamble and that I consent to it. If not, I’ll stand by my principles of not allowing my kids, especially if underage, to gamble, but that would mean letting the win slip away. I don’t know, maybe it depends on the amount. If it's too big, even for me, maybe I’d allow it. Or if he/she is still in overall positive profit. But if it doesn’t even break even with his/her overall stats, nah, I’d leave it as is, because he/she will likely lose more if I allow it. Better to leave it be until he/she reaches the legal age for gambling. The winnings won’t disappear anyway unless he/she use it to gamble more.