I have been with my boyfriend for a few months now, and things are going well. We're both happy. It's second time around for us, we were together during the 90's but things didn't work out due to geographical distance and work time-table clashes. We keep in touch over the years but in a platonic way, although feelings were still there, we were both committed to other people.
Now his ex wants him back. She has only wanted him back since she found out about me. She has involved their 16 year old daughter who is now crying on the phone to him whenever he is with me. I have sympathy for the daughter, she has ASD and is under pressure from her mother who talks to her about the situation. I want to say she uses the DD, but I don't know for certain.
The problem is that I am consumed with pity and guilt. He says he doesn't want to go back, but I can't bare to be the one that sets his daughter back to where she was a few years ago, a cloud of anxiety and depression, on suicide watch. 
I have three on the spectrum, one of whom has problems with anxiety and depression. So this is really very difficult for me. I love him, but I can't do this to her. Should I walk away?