"Steve. Steeve. Steeeeve." You whisper it softly, close to his ear, warm breath against warm skin. You trace the slope of his cheek and the angle of his jaw with the tip of your nose, count the freckles on his skin, breathe the rhythm of his dreaming. His eyelashes flutter and you watch them tangle and untangle as he pouts in his sleep, rousing slowly because he trusts you to keep him safe, to watch out for him. And it rips your heart out every time, that this super soldier, this literal pinnacle of physical perfection, this truly good man chose you, Tony Stark, the former merchant of death. "Steve," you whisper again and kiss his cheek, softly, a bare hint of contact because you do and don't want to wake him.
"Mm, Tony?" he mumbles, shifting slightly against the sheets, blond hair wild on the pillow as he nuzzles into its softness. "Wha's wrong, time issit?" he slurs, still asleep. There's a pressure in your chest, something deadly and life-changing wanting to break out, burning at the back of your eyes and thick on your tongue. It makes you rest your forehead against his temple and breathe out slowly as his eyelashes flutter against your cheek.
"No, shh, nothing's wrong," you reassure him, sliding a gentle hand down his arm in soothing motions. He relaxes back into the pillow and blinks, sighing a little as he wraps an arm around you.
"Too early," he mutters, turning his face into your shoulder, effectively cuddling and you let him. You smile against his neck, nip a kiss to the skin behind his ear, loop your arms over his shoulders and hang on. Then, thus prepared, you take a breath.
"I love you, Steve," you say, the words soft and quavering, but meant, sure and strong and unchanging - you'll always love him, no matter what.
"Tony," he breathes, blinking against your neck and trying to pull back to see your face. But you can't let him do that - you can say the words and mean the sentiment, but it might just kill you to see his reaction. So you hold him close until he stops struggling, just lays there breathing your name in what kind of sounds like dazed wonder.
"Happy Birthday," you whisper into the curve of his neck and feel his whole body relax with the realization of what you've just given him, what you finally managed to do for him, just for his birthday.
"Oh, Tony," fills the air around you, in you, warm with Steve's steady fondness, his trust and acceptance and respect, God, how do people do this, love somebody this much, a gnawing ache in the center of your very being? "I love you, too."
You cling to each other until the sun rises full and bright in the sky, until this thing, this leap of faith and proof of life, solidifies firm and unbreakable in the clear light of a new day.