A concept:
Gabriel calling Sam his sunshine puppy,
Because his smile brightens a room, and makes his day.
Because he wakes up so early,
And because when Sam is happy he can't stop smiling, and he just glows and gets so excited.

Gabe calling Sam his wings, because he carries him when he can't stand, and makes his heart fly, plus they are gold so they are the sunshine too.

Sam reading Gabe 'Good night moon' when he won't pretend to sleep. Sam knows angels don't need sleep but Gabe likes to cuddle with Sam, it makes them feel safe. Sam has always loved that book, and because Gabe is his moon. He is the light he in the darkness, even when there are other stars Gabe shines the brightest.
When Sam fist called him his moon, Gabe smirks and says "I knew you loved my ass"

They adopt a daughter and name her Celeste. She is their princesses, and they are there always for her, for everything.
Her first smile, first laugh, words, steps
Sam always managed to catch her before she fell, while Gabe would pick her up and tickle her till she laughed, and he let her try again.
She was perfect, sassy, snarky, loving, caring, and theirs.
She loved "unkie de" and "ca" and was best friends with their kids.

A concept:...
Sam got old... He had an amazing life... No, it wasn't perfect, there were fights, death, goodbyes, heart breaks, and so many tears. But he wouldn't want it any other way. Because even when there was bad, there was so much good.
He's a grandfather now, and great uncle. He had so many adventures and his husband doesn't look a day over 36.
Gabe is holding Sam's hand.
A thin hospital blanket covering his exhausted frame. He's old. Not sick... No evil creature taking him away too soon... Just peace.
It's time. Gabe can tell.
The family has said their goodbyes, Dean is already gone, they're letting Gabe have the last goodbye.

Gabe is quietly singing "you are my sunshine" he used to sing it to tease him. Sam smiles, his laugh lines showing. That's all Gabe wanted to do.
"...You'll never know dear how much I love you... Please don't take my sunshine away..." Gabe had a small smile on his face. Sam asked him not to cry. So he did his best not to. Not yet. Not till after he said his last words...

His voice was so soft before he left. full of happiness, and exhaustion.
"Goodnight moon..."