Like others have said, she's in her own place and your parents can't make rules for her at 23. Yeah, you'd feel better about it if she was married, but that's not what she wants right now. If you've been close and always trusted her to do right, this can be hard for you, but it's just how it is. The condom thing was really childish and it kind of looks like you're jealous and angry that this man has taken her away from you. But you're not going to get him to go away--she'll decide that. But try to get to know the guy a little, if your sister likes him, he's probably a good guy.