Rainbow and Soarin borke up shortly afer Iris was born. It wasn't anything like an ugly broke up or a huge fight. They just realized that their relationship wasn't working anymore so they decided to part ways so they are still on good terms. Rainbow took it upon herself to be a responsible mother and make sure nothing was missing from her daughters life. Being a Wonderbolt started weighing down on her tough so Daring Do came to the rescue. Being a writer and working at home gave her the possibility to look after Iris and soon the little furball took a liking on her (and her amazing bedtime stories) and would refuse any other babysitter. Daring didn't mind of course so they just continued their routine, sometimes with a tired Rainbow Dash in the background, falling asleep before the story even started.
I ship these two way too much sorry. Also this has been sitting in my stash for sooo long I don't even know what happened.