4 kids Dean doesn't know he has and 1 he does
They were both too young and Jennifer was his first. They didn't know what the hell they were doing; fumbling with each other, kissing, groping each other in the back of the school bleachers. She was wearing a skirt, hiked up to her waist, panties pushed to one side. His jeans were unzipped, dick out and straining, pushing at her, missing a few times, instinctively trying to get to where it was going. Dean no sooner slipped inside her than he came. Just like that, all the wonder and curiosity and frantic need; it was over almost before it began.
They fixed their clothes in a hurry, neither of them looking at each other. A quick kiss, a promise to see each other the next day and they went their separate ways. Talk about disillusionment; it was the most humiliating experience Dean had in his life. When he got home it was to find that his dad had packed them all up and were heading out of town; another hunt, another school, a new beginning. Dean never looked back.
Nine months later, an 8lbs, 2oz healthy baby boy was born to Jennifer. With the encouragement of her parents, she'd given him up for a adoption to a loving couple that couldn't have children of their own. They named him Joseph, after his dad and called him Joey for short. Joey grew up never knowing he was adopted.
Four months after Dean had come to help Cassie with the thing that killed her father and his closest friends, Cassie found out she was pregnant. She was young, had her entire future to look forward to and did not need the added complication of an unwanted pregnancy. It was while she was parked across the street from the abortion clinic that she decided there'd been enough death in her family, and instead drove to the nearest outlet store and bought a baby rattle and some diapers. These she presented to her mother, who genuinely smiled for the first time since her dad had died.
She admits to cursing Dean a few times during delivery, because he couldn't have just knocked her up with ONE kid, he had to have left her with TWO; A boy and a girl, 5lbs 7oz and 6lbs, 2oz respectively. She named them Samuel Martin, and Deanna Kathleen. She thought about Dean when she held them in her arms for the first time, and idly wondered what he would think, what he would do if he knew about them? She was pretty sure he would be smug with pride, and she was just as sure he wouldn't stick around to see them grow up. She thought about what she'd tell them about their dad when they were old enough to ask and the only answer she could think to say was that they had loved each other very much once upon a time.
Sammy and Dee gang up on her when they turn 15 and demand to know more about their father. Cassie knows full well what secrets and lies can do to a family. So she tells them everything, all of it, who their dad is, what he did for a living and why. She also tells them that he and their uncle died in an explosion when they turned 2.
Lisa watched as Dean walked away from her house, walked away from them, walked away from his son. She had lied, yes, but she had done it for Ben, just like everything she'd ever done since she found out she was pregnant. She had cleaned up her act, got a steady job, saved her money and bought this nice house in a great neighborhood. Made sure Ben had everything he needed, and in her mind, she knew he did not need a father, especially not one who did such crazy and dangerous things for a so-called-living. She closed the door behind her, watching as Ben happily played with his latest video game and knew she had come to the right decision. Dean was best left as a good memory, somebody she'd be forever grateful to for giving her a gift, two gifts actually, if you count fathering Ben as the first and then saving him from that monster as the second.
When Anna opened her eyes and found herself back in heaven, she was surprised to find that she still was in her human body. Pain flared in her belly and then she knew why. It was supposed to have been her last night on earth, the last time she could love and be loved, to make love and rejoice in all things that were human, in all the things she loved about humans and being human. So when she seduced Dean and they made love to each other in the back seat of his car, she never once worried that they had not used any birth control. When she took back her Grace from Uriel, her own power shielded her human body, protected that spark of life nestled deep inside her womb. Heaven and its angels have done many things in the name of God, murdered innocents for the greater good, but for some reason, this one innocent she carried within her was to be spared and that scared Anna more than she could say. But she carried on with the fight, good soldier that she was, and asked no questions and waited for no answers.
At the end of the final battle, when the seals were all put back in place, after Lucifer was thrown back into the pit, two brothers, beaten but still alive, Castiel came to Dean one last time. In his arms he held a naked, still bloody from birth squalling baby girl. He handed her to Dean, placed his palm on the side of Dean's face, looked him in the eyes and told him, "Anna wanted to call her Abigail. It's a good name. It means 'My father rejoices' in Hebrew."
Dean looked down at the squirming baby in his arms and when he looked up, Castiel was gone.