I agree with the above. Boundaries are being crossed and it’s highly inappropriate. Though I’m confused. Are you married? You call him your boyfriend, not husband, but you said she’s your step daughter. If you’re married then I would say you have the right to bring it up to him. If you’re not married, then it’s not really your place to say anything. He’s the one who should set the boundaries and not allow such inappropriate behavior. It’s most likely because he was absent from her life for several years. Why was that? Something is very off about all of this.