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As far as I know alcoholism can be transmitted on a genetic level as this disease affects genes, destroying them. You can easily notice it in families which have an alcoholic father in the head of the family and live in poverty. This is unlikely to happen with gambling as it only affects a person's psychology. So if you are into gambling it does not mean that your children will have the same hobbies.
So I dig further and I learnt that genes can modify and since alcohol is a combination of different chemicals if it is abused with time, it can affect the offspring, so I take back my previous example as a case study with heredity but gambling hereditary says otherwise. Although, it can be transferred from parent to children but the percentage is quite low and again, if the child stays with the addicted parents is likely to happen than when they are taken away from them. Literally, if an addicted gambler gives birth to a child and its been taken care of by another caring parent, the chance of the child becoming a gambler will be very low.