The worst part about humanity was aging. Sleep and the last half of the digestive system irked him for years but after over four decades as a human he could declare old age as the worst malady with authority. Just when he was got comfortable with his limited human endurance his hair turned silver and his joints started to make unpleasant noises.
According to Dean he remained incredibly handsome even after needing hip surgery. Dean aged gracefully. Although Castiel caught him several times frowning at his thinning hair in the bathroom mirror.
The only good thing about getting old was watching the children mature. Dean denied it but he cried at every wedding, Castiel didn't, and the first time he held their first grandchild. The circle of life was completed as Castiel and Dean were driven places and cared for by the children they had raised.
Sam's family was only a few years behind them. Sam kept his drivers license after Cas and the kids finally pried Dean's out of his white knuckled grip. He didn't need to worry so much, the Impala was loved by two children equally and they argued over its ownership and care endlessly.
Dean died before Castiel. Although lonely, he didn't grieve for his mate, he knew he would join him shortly. It would be sad to leave the children but he had done his part, they were prepared to live without him.
He closed his eyes in the hospital bed and opened them on a grassy hill overlooking a calm lake. He smiled as he recognized the calm vacation spot his family had visited. Dean had taken the children fishing and target shooting.
Cas took a moment to enjoy the scenery then headed towards the lake in search of Dean. They were soulmates, they would share a Heaven. At the crest of the hill he spotted Dean sitting on the dock with a fishing pole, a case of beer and an empty chair sitting by his side. He smiled and opened his mouth to call out to him.
"This is beautiful." Castiel sprung around at the familiar voice. "You took my advice."
"Metatron." Cas froze, the last time he saw this man he had sliced his neck and stole his grace.
"I'm here for your story, Castiel. It looks happy."
"Hey!" Metatron turned and saw Dean storming closer. "I said, 'wife'." Metratron said only to have Dean punch him in the face.