I like to gamble, but I never tell anyone, especially my family like my older sister. It's just that one day I heard her gambling and how happy she was when she won, this actually surprised me because I knew she liked to gamble, as time went by she always did it, actually it was her own right, only I was afraid that something unwanted would happen, especially since she already had children to take care of. What I thought was that she knew about gambling because currently gambling advertisements are everywhere, coupled with her own difficult economic situation, it was only natural that she was tempted by the victory in gambling so she did it. What's worse is that my older sister's husband also likes to gamble, this is concerning and worrying.
It shouldn't be concerning if they are not addicts, some people gamble to get lucky and they are able to do it moderately. Whenever they win they accept their wins happily and whenever they are losing they just walk out instead of going all in. If your sister and her husband are gambling like this then there's nothing to worry about. The only problem might be when they are addicted gamblers, if this concerns you have a friendly chat with her