Do not -I repeat- do not read any of twentysomething's fics unless you want to be slayed by how adorable they are.
I happened to stumble across The Manny Diaries first, which is something of a The Nanny Diaries AU, except with some plot changes (like Dean thankfully being nothing like Annie). The summary is as follows:
Dean has always thought kids were great in an abstract kind of way- he enjoys monkeying around with them, and they- for who knows what reason- like him, but Madeline Meyer stole his heart on a rainy Friday afternoon when she solemnly marched over to him, plopped herself down next to him and told him that Miss Moore had told her that Dean knew why cars worked and she wanted to know, too.
I really enjoyed reading it. Although Dean is kind of dragged into working at a preschool, he adores Madeline and they get along so well that I have no idea what to do with my feelings. And then, one day, Dean meets Madeline’s father, Castiel.
He ends up becoming Madeline (and her little sister, Isabelle)’s caretaker and moves in to the Meyers’ pool house, “which is secretly a guest cottage, because the real guest cottage is secretly another house”. He’s also insanely attracted to his boss and Castiel obviously feels the same way, yet the way they misunderstand each other and dance around their feelings makes you want to scream at them to have sex or get married.
Which leads me to It’s Only Monday, Mr. Mom, a crime against humanity because the domestic fluff is so wonderful while still being in character that it makes me weep. Basically, Dean ends up meeting Castiel at a summer picnic the law firm Sam works at is having. Then suddenly they’re married with two of the most adorable children ever (a girl and a boy named Susanna and Teddy) and it’s just not fair how perfect their family is. (To be honest, the one issue I have with the fic is that it’s never explained how they have kids. But then, in the grand scheme of things, I suppose doesn’t really matter.)
And then there’s This Is Not A Test, which is sort of like Mr. Mom, except Dean and Castiel have three children (a daughter named Abby and two sons named Jack and Max). When the three of them come home from school one day, they find a dead body in the garage and their fathers are missing. Then Uncle Sam and Bobby arrive on the scene and end up having to explain that Dean and Castiel are actually a hunter and an angel. And Abby, Jack, and Max realize that their “ordinary” family isn’t quite as ordinary as they originally thought.
But at least it explains where they come from, despite lacking a mother.