Tony: You both have a star on the Hollywood Walk of Fame. It's a pretty big accomplishment for both of you, plus your stars are right next to each other. You guys go and see them when you're on vacation, and you always take a picture with your hands holding on top of the star.

Steve: He has a star on his shield, and you have a matching one sowed onto your jacket. So, whenever he was away on missions, you had a way to feel better when you felt lonely.

Bucky: Bucky has a star on his metal arm, and you have a matching one one your hip. You knew how Bucky felt about his arm, and you also had a huge fear of needles. But that didn't stop yoi from getting this tattoo and proving to Bucky how much you loved him.

Bruce: You both have a star charm on your charm bracelets. Yours for being a star on stage, and his for being a 'star boyfriend', in your words.

Thor: You love astrology. It was your way of forgetting your past. So, every other night, you and Thor would stargaze on top of the tower.

Loki: He has a star ring, and you have a star necklace. It was to remind each other that you were both worth it, and that you both were each other's star.

Peter: You both have 'Star Student' stickers, that made you both laugh during hard times.

Clint: He has a pair of star-sunglasses that you wear all the time. He doesn't mind that much, but only because you look really cute in them.

Natasha: You both have a t-shirt that says "The woman next to me is a star" You wear them all the time, and you laughed so hard when Nat stood next to Tony.

Wanda: Wanda has a small star tattoo on her wrist, so you decided to get one there as well. It made her super-duper happy.

Pietro: You have matching tank-tops that have a star on them. You wear them to bed, and to the gym. It's pretty cute, actually.

T'Challa: He has stars on his crown, and you have stars on your crown. They are really tiny and hard to see from far away, but you both know that they are there.

Scott: You both have drawings of stars. His are from both Cassie and you, while yours are from your own hand and Cassie. You both cherish all of them, for they remind you of eachother and Cassie.

Sam: You have a star named after you that Sam gave you. It makes you both smile, and you kiss him every time you see the certificate.
Sorry if this is really bad. Kind of stuck in writer's block right now.