Sam and Dean don't remember their first kiss.

Sam doesn't remember a time without eyes brighter and greener and more beautiful than any emerald could hope to be starting back him with love so infinite it nearly brings Sam to his knees.

He remembers their first kiss after their first time making love, Dean gently and effortlessly loving Sam in the backseat of the Impala. The first time Dean kissed him while tears fell down his face, after finding the letter from Stanford in his duffel. The first awkward but still amazing kiss after Stanford. Their first kiss after dad died. The first kiss Dean nearly tackled him with after Cold Oak. Their first kiss after Dean came back from Hell, like a dream but so bittersweet. The first kiss after Sam came back from Hell. Their first post-Purgatory kiss, filled with so much anxiety and fear and desperation. Their first kiss after realizing that they are two halves of a whole, better together than they could ever be apart.

Through a lifetime together, they've shared thousands upon thousands of kisses. And they'll share thousands more.

Good morning kisses, goodnight kisses, I've missed you kisses, It's okay I'm here kisses, it was just a nightmare kisses, I need you I need you I need you kisses, onion-breath kisses, please don't leave me kisses, you're a dork but you're my dork kisses, I thought you were dead kisses, I still love you kisses, just because kisses, I can't believe you're back kisses, take your clothes off now kisses, goodbye kisses, perfect kisses, sloppy kisses, angry kisses, I'm sorry kisses, high on adrenaline kisses, you're mine kisses, barely there kisses, toe-curling kisses, life-affirming kisses, electrifying, soul-deep kisses.

Sam and Dean don't remember their first kiss.

It was probably before they were even born.