Ask Amy: This is a no-brainer in my opinion

Trust your gut, lady. You love your sister and you don't trust her boyfriend. And why would you expose your young child to an illicit, shack-up, temporary relationship anyway?

She [sister] has now met a “new” guy, and much to our dismay he quit his job and she has been supporting him for about a year. He has since gotten a part-time job and is taking courses to better himself.

However, he is temperamental and often loses it in our presence. My sister says his temper is short-lived and that he is working on it. A few times he has verbalized little digs at my kids when he does not approve of their behavior and I’ve let it pass because we don’t see them very often

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Ask Amy: Sketchy boyfriend worries family members - The Washington Post