Captain America, the ultimate symbol of freedom, bravery, and the entire Marvel Universe, has shown in the past that he will stop at nothing to protect those who cannot protect themselves. His altruism knows no limits, even going so far as saving the life of the son of one of his greatest enemies, Arnim Zola. To Steve Rogers, life is precious and the duty of a soldier is to give their lives to protect those in need, and when given the chance to save the life of a child, it didn't matter who its father was -- it was just an innocent bystander wrapped up in Zola's twisted games.
The character, Arnim Zola, was created by Jack Kirby and first appeared in Captain America #208 in 1977. He is a master of biochemistry and one of Captain America's greatest enemies. He was a Nazi in WWII but survived into the modern age by transferring his consciousness into a robot. Zola spends most of his time attempting to steal the Super Soldier Serum from Steve and use it to create his own league of superhuman Nazis.
In Captain America #1 by Rick Remender, John Romita Jr., Klaus Janson, Dean White, and Joe Caramagna, Steve Rogers enters the mysterious Dimension Z and is captured by Zola. Dimension Z is an alternate world created by Zola full of mutates and insane technology. In this dimension, time and space work differently than they do in the normal Marvel Universe. Time moves much more quickly in this world, which causes people to age rapidly. Zola captures Cap and attempts to use a huge syringe to take his blood and make a Super Soldier Serum.
As Steve regains consciousness, he sees a figure in a test tube and realizes that Zola has grown his own son and attempts to turn him into his own version of Captain America. Steve narrowly escapes and takes the baby with him. The baby is known as Leopold, but Cap decides to rename him, "Ian Rogers" and raise him as a hero.
Cap raises Ian and manages to protect him for 11 years inside of Dimension Z, but tragically in Captain America #8, Ian is shot and apparently killed by Sharon Carter. At the time, Ian had been brainwashed by Zola into hating Steve and trying to kill him. Steve was unable to attack his "son" so as Ian was about to do the killing blow, Sharon came out of nowhere to shoot Ian in the neck. Cap is heartbroken at the loss of Ian, and he escapes Dimension Z and returns to his world. In Captain America #10, the same gray version of Cap's shield that was used to almost kill Cap in Captain America #8 is being used to mow down Zola's mutates. It is then revealed that Ian survived and is now going by the name, Nomad, and sports his own version of his father's star-spangled suit, taking his father's place as the defender of Dimension Z.
Later in Captain America #22 by Remender, Carlos Pacheco, Marino Talbo, Dean White, Lee Loughridge, and Lauren Sankovitch, Steve Rogers has changed due to his time in the alternate dimension and is now a very old man. Suddenly, a door to Dimension Z opens up in Central Park and with it comes the disgusting mutates of Arnim Zola, as well as a single mysterious figure clothed in a suit of armor. In Captain America #23, the figure deftly fights multiple Avengers to work his way towards Old Man Rogers. With the iconic line "I was taught to always stand up" the man removes his helmet and is reveals himself to be Ian Rogers, Steve's lost son. He explains that he survived by falling into Zola's Bio-Mass tank -- the same stuff that was used to create him -- which allowed him to regenerate from the gunshot.
After the events of this issue, Nomad went on to fight alongside Sam Wilson after Sam became the new Captain America. The two had a tense friendship as Nomad thought Sam was unfit to be the new Captain and that he should have taken up the shield instead. Nomad was included in both the "Axis" and "Secret Wars" storylines and is still out there in the Marvel Universe. Perhaps Captain America's son will be seen more in the future, and maybe even one day hold his father's shield.