Very upset about my sister' mothering...am I jealous or concerned?

The only thing your sis has is a son she can't take care of. It's great of you to offer to take them in, but maybe you should just extend the invitation to her son. Tell her you'll take him for the summer or a couple of weeks and that it will give her some alone time with her boyfriend. You could use the time with him. Her life is nothing to envy. She's a deadbeat. You can still have kids. With a 6 fig income, you could even adopt. Stop being so bitter about your past. That's what it is--the PAST. Adopt a better attitude about yourself. You are a success in spite of your past. You should be very proud of yourself. Find someone who treats you with the respect and kindness you deserve. Meantime share your generosity of spirit with your nephew.