What if someone was addicted to something that is harmful to themselves, and if they found out, harmful to their family aswell?

A common issue: I don't fully understand your question, but it's very common for people to be addicted to harmful things and, once they realize it, important to seek treatment. When 1 person in a family is addicted it harms the whole family, but addictions often run in families so many in a family may have the same addictions. Keeping addictions a secret helps no one; it is better to be open about it to get help.