Can guys change when they in love?

I have a friend that I am really close to, even I like him and he knows, but I just found out he is been having sexual things with a girl I know over video calls, when I confront him, he said they had in the past that it was truth but ever since he met me, and started to have a crush on me he started to change and not talk much with that girl because he doesn't want to lose me... but yet the girl blocked him and she is telling me to get away from him since he could be like that with me...

Can guys change when they in love?
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