actual parents sam and dean
when you invite your friend over and then your dad insists on being so weird and of course your nerdy uncle (who basically never leaves anyway) is there too
THE DESTIEL DADS THING SORT OF HAPPENED RIGHT???
What do you mean “sort of”???
(excuse me I am still hyperventilating :P)
Dean parented the crap out of Claire. He and Cas got her terrible dad presents. He and Cas discussed how Cas was related to her. Sam and Cas discussed how Cas was related to her. If we apply the found family rules Dean set down to Crowley very recently as a reminder that you make your own family, we saw Cas at least working extremely hard to be the best little Dadstiel he could be. Cas was Dadstiel by the end of that episode at last.
And then Dean paralleled him with his dorky presents (which Sam didn’t do).
And he was giving parenting advice like do your homework and yeah that was about murdering monsters but their whole little adventure was an allegory about the importance of doing fucking homework, like, this could have just been a weird show about two guys who adopt a kid and use monster hunts as allegories for enforcing generic parenting advice. And Dean being the one to say “take your daughter to work day” - seeing as he was the one who blurted out that line, not Cas, it put him in the “dad” role as well there even before he turned the parenting up to 11.
There was no specific link between Dean and Cas being the dad at the same time, but both of them dad-ed the hell out of Claire. Claire had 2 dads by the end of that episode and they were Dean and Cas.
But what about Sam? While Cas and Dean were being awkward and asserting their position about being the dad figure in her life and generally having a really awkward time where they both worked to relate to her and fill a space and give her presents and negotiate really awkward dad problems, Sam was more impartial, calm, not worried about the impression he had to make on her and didn’t do anything overtly dad-ish for her. He looked after her and advised her and helped her and taught her stuff, but on a much more equal footing where they talked together and his emotional experiences helped her yadda yadda.
It was so not a dad story for Sam. He was being the cool uncle who Claire can go to when things are too awkward with the dynamics of the father/daughter relationships to make the conversation come easily.