This guy, Bucky Barnes, is the MCU version but he's got a lot of love for his BFF Sam that he won't admit to. He'll be shocked by the Cap situation and have questions. He's coming from point in Infinity War where they're gearing up to battle so he was probably just with his version of Sam a few minutes before he arrived. We should have them meet up soon!
I also have Remus Lupin (lonewolfen) from the Harry Potter books. He's coming from a handful of months after the First War, very jaded, but getting better having been around his friends (well, one is now gone, but the other is still here). He's generally pretty polite, has a sharp wit, and would be kind to Sam.
Next is Thor (MCU) who is coming from literally right when Thanos snapped his fingers. He is a very sad boy. Like, slipping into PTSD but has no idea it's happening. He kind of goes between shouting in CAPSLOCK on the Net out of merriment and slipping into brooding moods when he's alone. He doesn't know his version of Sam that well but generally like likes the Bird Man -- yes, he'll probably call him that.
Last but definitely not least, I have Gwen Stacy aka Spider-Woman aka Spider-Gwen from Earth 65. She's coming in from a botched mission to recruit a Peter Parker from the multiverse who died trying to protect her. After already losing her own Peter Parker back home. She's got some issues, but overall she's really a pretty nice person. Sarcastic and sassy, but always ready to help anyone with anything. In her world, Captain America is Samantha Wilson and she is one of the few people in her world who actually likes Spider-Woman and vouches for her being a good person so she'll definitely like Sam. And want to be his friend.