It may mean that she wanted to see who you were and could not do that without adding you as a friend, either she no longer saw you as a threat or she didn't see anything in your profile or didn't find what she was looking for. Also her husband your ex class mate could have asked or told her to delete you as a friend and that your weren't a threat if you want to keep her as a friend try requesting her as a friend and see if she accepts if she doesn't then I would let it go. If you have anything to add click reply.
Either he told his wife or his wife some how saw what you said, you have to be careful when emailing someone that is married that you don't put a strain on his marriage over a high school crush. My advice to you is if you can not be friend with both him and his wife then it isn't a good idea to keep contacting him especially if he asked you not to email him anymore and then two years later you emailed him again. You don't want to come off as someone trying to make trouble in his marriage or someone that can not let the past be the past. Since you both are married now I suggest leaving it alone he didn't reply instead his wife added you as friend probably to see what you were about and may have been contemplating contacting you about contacting her husband but perhaps her husband talked her out of it. I would let it go at this point and just chalk it up to the past being the past and look to the future with your husband.
It is more complicated because he did the same thing to my husband 10 years ago. He wasn't married at that time but I was and still is. Besides in facebook, she could have looked at my photos without any problem because he and I have networks together. He and I run races and he has been here 3 consecutive years after he found out that I liked him after 20 years. Also, his wife is a mirror image of me. He ran the last 2 races with a wedding ring and this year he didn't. I hadn't emailed him but just this recently. So what does that mean?
I can not answer for him what that means only he can answer that but my opinion is that his wife being a mirror image of you maybe a mere coincidence or subconsciously he figured if he could have you then he would have someone that is close to being you looks wise. Him running the race without his wedding band could mean many things, he doesn't feel comfortable running with it on, he left the ring by accident, he could be separated, he could just choose to no longer wear a ring. The fact of the matter is you are both married so what is the point of re hatching your feelings unless you just wanted to get that off your chest and move on. Still if he doesn't reply to your email then that may mean he wants no parts of how you are feeling because he is married and he knows that you are married.
What you have to decide now is if you want your marriage to last and if so then you have to let this go and concentrate on your marriage and if you can not get over this guy then maybe you should be honest with you husband about the way you are feeling. This guy from high school may not want to concentrate on what you told him because he knows you are both married to other people and he doesn't want to cause any problems or break up a marriage. You may need to talk to him face to face to get the answers you want from him but only he can answer why he married someone that looked so much like you and why he doesn't wear his ring.