Do men know when they've met "the one"?

My fiance said to me the other day that when we met, he just had this overwhelming feeling and sense to "take care of me" for the rest of his life. He said it was "game over" and he knew he was "done" when we started dating and that it was a feeling he just couldn't explain. I find that to be the single most sweetest thing anyone has ever said to me. Yet, I'm a very guarded person and I don't talk about my feelings that much. He tells me it's ok to be vulnerable sometimes and allow myself to feel things but with my relationships and friendships, I just never trust that anyone is 100% able to love and be loyal to someone for the rest of their lives. So is it true that men really do just "know" when they want to love one woman for the rest of their lives. I've never been more in love (only been in love once before him at like 18 years old) so I knew when I met him that I wanted to be with him. We are both almost 40. Both divorced. Been dating for 1 1/2 years and are living together. I love him and can't picture my life without him. I'm just guarded and don't know if I believe that a man can love someone and be loyal forever. To note: we both got married to our previous partners at a young age and because we had kids with them so we felt obligated. It was never love with them so when he says he wants to get married and even have more kids, it makes me nervous bc this marriage would actually be doing it because I'm in love. Do men really get married because they love that person and don't want to look for anyone else? Do they get that feeling of not wanting to look anymore and wanting to take care of their wife for the rest of their lives?
Do men know when they've met "the one"?
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