I feel sympathy for Terry. The poor woman is in a lot of pain! Bravo to her other son for standing up for her! 
 
Just shy of our 25th anniversary, my husband decided to "call it quits and go our separate ways" (as if we were only going steady or dating!) I asked if there was someone else and he lied (that came really easy for him) and said no. I found out a little later that he had been seeing another woman his own age for about 13 years. After we separated, he started "dating" her, introducing her to our teenage daughter and his son, from his previous marriage, as his new girlfriend.  
 
I met him while I was working as a waitress to put myself through college. I was a very young 21 year old innocent, who never dated or had a boyfriend, partly because I was shy, but mostly because I only wanted a career. (Not because I didn't look good: petite 5'2", 105 lbs, long blonde hair, green eyes, nice teeth....more than just my mom told me I was beautiful). I was a talented artist. He was 5 years older, a divorced cop and father to a 5 year old son. He relentlessly pursued me for months (didn't realize at the time but it is called "stalking" nowadays) until I finally dated him. He was very generous and loving to me, saying the nicest things about how he would love me forever and ever, and all that. I told him I didn't want to get married, but somehow we ended up getting married. 
 
After our marriage, he changed jobs and made a great salary, I couldn't find a job in my chosen field (art/graphic design), which he didn't seem to mind that much since he was afraid some guy would steal me away. He was very controlling and posessive. He made Scrooge look like a spendthrift. But only I was witness to his miserly ways. He kept telling me he had to save money for our old age. I would get upset when we would go out to dinner with people and he would try to pick up the check, but at home he wouldn't give me 5 bucks.  
After marriage, I noticed he didn't seem to like his mom. Found out later she was a tramp (to put it nicely) who was a rotten mom. His parents divorced when he was 8. He didn't seem to know what her birthdate was. So I asked her, and every year I would remind him to wish his mom happy birthday. (Funny, years later, she bragged how he always remembered her birthday.)  
When his dad was dying of cancer, I took his dad into our home and took care of him. His dad left him a lot of money. He was still miserly to me. 
 
After I had our daughter, our marriage really took a nose dive. He started to bug me to get a job. I did some freelance art work. When my daughter started school, I took a menial job which was all I could get because I hadn't worked outside the home since college. I was paying for my own car, expenses, clothes etc. 
 
When his mom had a heart attack, she asked my husband to take care of her finances. He found out how much money she had and then he played the dutiful son. He would visit her a lot, got power of attorney....She used to annoy my mom and friends with her comments about how I had it so good and her son was such a 'good provider'. She would point out how I had all these things. (Well, I bought them with my money.) When she got cancer, I helped take care of her for a short while before she had to go to a nursing home. She died and he got a lot of money. About 10 months later, he left to be with his longtime girlfriend.  
After he left, he started to call our daughter every day and buy her things and take her out to eat. I thought it was about time. It looks like he didn't know how to be a father, but knows how to be a divorced father. 
 
The divorce took 2 years and it was costly, horrible and stressful. He had all the money he stashed over the 25 years (money he saved because of me), plus his inheritances, but made it look to the Court like he was poor....He filed petitions about trivial nonsense, had his lawyer keep sending my lawyer letters....anything he could think of to cost me money (lawyers charge for every single phone call, reading and sending letters etc.) We only had communication through the lawyers. I don't ever want to see him again. My daughter is a Sophomore in college and is on the Dean's List. She is beautiful and an extremely brilliant, talented writer. So far, she has never had a boyfriend....she is focused on having a career. 
She now has a good relationship with her father. She thinks I should just forget all about the past and gets upset when I even mention her father. It is difficult to erase more than half your life. I'm trying. It takes time. If my daughter gets married, I would not disrupt her wedding, but if someone asks me why her dad and I don't talk to each other, I may tell them.