If you asked them, neither Mac nor Rainbow can really remember when they started dating. They met after the longest night in a thousand years and their connection to Applejack brought them together with some frequency. At first, Mac was just Applejack’s brother and that was it. She would try to get a rise out of him sometimes, egg him on, things like that. Conversations over drinks at Apple Farm parties and stopping to chat as they ran into each other brought them closer. Rainbow used Mac kind of like a diary, telling him about things. Even if he didn’t say anything, it felt good getting it off her chest. When Rainbow hit the peak of her Wonderbolt career, seeing most of her friends getting married and starting families made her start thinking about that kind of thing. When she decided to ask Mac out on a date, she realized that was what they were basically doing already, sort of. They just had to make it official. A short time later, Mac proposed.  
They have two daughters. I haven’t really developed them a lot yet. The first is about as girly as you could possibly get, the second is ADHD enough to give Pinkie a run for her money.  
I was inspired for this style of humanization by a piece by ThePandaCaffe. However it’s actually the second time I’ve drawn using this humanization style. I drew a quick SoarinJack at work recently, but I wanted by first posted work to be MacDash. No, Rainbow’s wings aren’t missing. I like the idea of wings just magically being summoned. I’m sure they’ll pop up when he kisses her shortly.