Even though the MCU's Captain America knew that Iron Man's parents were killed at the hands of Bucky Barnes, a.k.a. Winter Soldier, he didn't tell his fellow Avenger before the events of Captain America: Civil War.
Captain America only knows the Tony's parents were murdered by Hydra, he didn't know that Bucky was the one to make it happen, but what he knew came from Armin Zola, or at least the computer housing his personality, in Captain America: The Winter Soldier.
What did Captain America find out in the Winter Soldier?
Steve Rogers, finding it easier to acclimate to the modern society as a soldier of SHIELD, learns that the organization has been compromised and a Soviet assassin known as The Winter Soldier will stop at nothing to kill Captain America, which leads him uncover a truth that will change everything.
Bucky ended up at the Red Room, an assassin training facility, where he participated in the Black Widow Ops program as a trainer—and that's where he met Romanoff for the first time. The two soon started having an affair.
Did Howard Stark know Bucky was the Winter Soldier?
Security footage from Howard Stark's death in Captain America: Civil War showed he knew Bucky Barnes was the Winter Soldier, but how did he know this secret? From the very beginning of the Marvel Cinematic Universe, it has been known that Tony Stark's parents died on December 16, 1991.
Bucky Barnes, like Steve Rogers, has lived for several decades due to cryogenic freezing and the super-soldier serum. Bucky's life expectancy could potentially surpass Steve's 116 years, depending on circumstances. Despite outwardly aging at the same rate as Steve, Bucky can still live for at least another 80 years.
Barnes aids the Avengers in the conflict against Thanos, falling victim to the Blip. After he is restored to life, he joins the final and victorious battle against Thanos. After Rogers' retirement, Barnes is pardoned by the U.S. government and strives to make amends for his murderous past.
Because the strong man who has known power all his life may lose respect for that power, but a weak man knows the value of strength, and knows compassion.” This is also why Steve chooses Sam to be the next Captain America.
There's no doubt disappointment over Bucky Barnes not showing up in Captain America 4, especially since Stan's character has become a beloved fixture of the MCU since his debut in 2011's Captain America: The First Avenger.
What's fascinating about the Cap-Bucky story as well is it's a love story. These are two guys who grew up together, and so they have that same emotional connection to each other as brothers would, and even more so because Bucky was all Steve had growing up.
However, while Tony did make amends with Steve, he wasn't able to do so with Bucky. In fact, they didn't even get to have any interaction before Iron Man's death.
The Winter Soldier Program was a top secret HYDRA project started by Arnim Zola in the 1940s to brainwash American soldier James "Bucky" Barnes, whom he had administered with his own version of the Super Soldier Serum, and turn him into a super soldier assassin known as the Winter Soldier.
In the comics, Howard and his wife died in a car crash, as the result of faulty brakes arranged by either business competitors Republic Oil & Gas or by V-Battalion. Howard's death inspired his son to take both business and engineering seriously as Iron Man.
While at the HYDRA Siberian Facility, Barnes' prosthetic arm was destroyed by Tony Stark's unibeam, after Stark was manipulated by Helmut Zemo and attacked Barnes and Steve Rogers.
He's a little more than a year older than Steve, which makes him the oldest human Avenger at a chronological 106-years-old. This puts him in his twenties during Captain America: The First Avenger, as he would have been about 26 in 1943, when he and the 107th were captured by Hydra.
In Captain America: The Winter Soldier, Bucky is shown to have survived his fall during World War II. However, the film was adamant about conveying to viewers that this Bucky was a shadow of his former self.
Conversation. Actor Sebastian Stan has shared this video of him and his friends celebrating the 107th birthday of Bucky Barnes (Bucky was born on March 10, 1917 in the MCU and would be celebrating his 107th birthday on March 10, 2024)!
We see that he's deprogrammed 6 months before the snap in FATWS. He's then snapped away and comes back 5 years later. FATWS takes place 6 months after he comes back. So Bucky is likely 33 physically while chronologically being 107 (FATWS takes place in April 2024, so Bucky's wrong about being 106).
Even Bucky's variant serum should allow him to age normally (unless he gets frozen again). A side effect of the Super-Soldier Serum that the Winter Soldier shares with Captain America is that neither can get drunk.
Bucky Barnes' love interests are few and far between in both the MCU and the comic book pages. One of the few serious relationships that Bucky built outside of the MCU was with his love interest Natasha Romanoff.
Black Widow's first romantic relationship was with Nikolai, a soldier she met while both were serving with the Russian Army during WWII. The young soldier had no backstory, but Natasha and Nikolai fell in love and eventually married.
The actor also said that Sam and Bucky's relationship is rooted in acceptance, appreciation, and love for each other. "You'd call it a bromance, but it's literally just two guys who have each other's backs," he said.
