Jack oftern thought about what his family looked like from the outside. He knew that they weren't normal, no not at all, he had three fathers for starters and not one of them related to him (by blood at least even if technically Cas as Lucifer's brother since Lucifer was once an angel too) and the other two were brothers. Next was the fact that he loked like a teenager but he didn't know anything about anything pracically, they would always have to expalin things to him when they went out but Jack didn't care. He loved his family and he wouldnt change them for the world (ok he might get Dean and Cas to get their act together but that's beside the point).
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Growing up with Dean pretty much taking the place of his mother and father while also being his older brother meant that Sam didn't actually care about what a typical family looked like. He had Dean,who had always been there when he needed him, Cas who he loved like a brother and he had Jack his son. Sure it was difficult at times, it was heartbreaking at others but at the end of the day they loved each other and they would do anything to protect each other and to him that was his perfect family.
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Dean didn't give a shit what other people thought of his family and if they said anything to him he would gladly break their nose for them (he had tried when he took Jack and Cas to get groceries with him and Cas had to drag him away from the goddamn son of a bitch that insulted his son). He had a son, after Ben he could never have imagined raising someone again, especially someone who was litteraly the spawn of satan but here he was and he wouldnt change a thing. He loved Jack and he would do anything for him, just like he would for Sammy and like he would for Cas, even if some traitorist voice in his head liked to remind him that the love he felt for Cas wasn't the brotherly sort of love but he quickly shut the voice up, not willing to even hope for the possibility Cas felt the same. Overall he loved his family and despite never expecting or really hoping for more than just him and Sam he was happy with his family.
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Cas never really knew what family was, yes he had heard humans talking about it and yes he call his fellow angels his brothers and sisters but really he had no idea what it really meant until he met Dean and Sam and saw what they would do for each other (and when he was piecing Dean back together he felt how much love Dean had for his brother, he got a glimpse of family). He knew, now at least, what family was and to him it was Dean, Sam and Jack, his best friend and the man he was in love with, his other best friend and his son. He knew that they weren't a normal family but he didn't care, he was happy and he knew that they were too, he could feel it radiating off all three of them and he knew he would take that knowledge with him for the rest of his time and cherish it.
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They weren't a normal family but they didn't care, they loved each other and would do anything for one another.