Is it wrong for a 21M to date a 17F?

I met his mom and he told her I was 18 at first but after only two days of telling her, he told her the truth, that we had slept together and I was actually 17, he said she wasn’t mad about the age thing but that he lied. Overall she was okay with us as long as there’s no more sex, she’s more worried about my parents pressing charges if anything. Although, my older sister dated a dude his age- maybe a little older like 23, when she was my age, and although my dad didn’t necessarily agree with it per se, he didn’t take any legal action and even let him move in at some point before they broke up. But even after all that I still have to wonder, is it really wrong? I mean it’s not even a 4 year age gap, he just turned 21 and still acts like a teenager, I mean sure he’s still mature and technically an adult, but for the most part he just acts like someone my age, he doesn’t even drink either so before anyone uses that against it saying “he can drink legally, you can’t” yes I get that. Oh yeah and I’m not in school anymore either before anyone tries to use that.
Is it wrong for a 21M to date a 17F?
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