Is it normal for my fiancee to secretly look at pictures...

my fiancee was secretly looking at pictures of his brothers girlfriends vagina before she was going to come over and visit while i was at work all day, we all get along fine, and we are all uninhibited freaks by nature so in a situation like that is it normal for a guy to be in love and stay faithful and have the desire to secretly look at photos of her vagina before they were to hang out together all day (also the brother is in jail and she used to be an escort).. should i be insecure?