Avengers: Endgame spoilers ahead. Avengers: Endgame viewers get a nice surprise when, after the five-year time jump early in the movie, a tiny Stark emerges from a tent in her backyard. Yep, Tony Stark and Pepper Potts had a baby following Thanos' big snap (apparently, directly following) and named her Morgan. But while the Morgan in the movie is a little girl with a very well-known father, there is also a Morgan Stark in Marvel comics, who has a very different backstory.
In Marvel comics, Morgan Stark is a man and a cousin of Tony's. According to Comic Vine, Morgan was first introduced in Tales of Suspense #68 in August 1965. The site explains, "Morgan has always been jealous of Tony's success and has attempted at least once to usurp Stark Enterprises from his control." Morgan is the son of Tony's uncle, Edward, who is Tony's father Howard's brother. IGN explains that Morgan thinks his side of the family was cheated out of their share of the company, which leads him to seek revenge, when, really, Edward willingly gave up his ownership. According to the Marvel Fandom site, this version of Morgan made 30 comic book appearances over the years.
As it goes with comics, though, there are different realities and timelines that make things more confusing. There is another line of stories in which Morgan Stark is the name of Arno Stark's father, with Arno Stark being Iron Man 2020. Then there's one where Arno and Tony are adopted brothers and Morgan is a cousin. But, basically, for the purpose of comparing comic Morgan to movie Morgan, all you need to know is that he's not that huge of a character, he's a Stark family member, and in his original iteration he's a jealous cousin of Tony's. Also, worth noting is that in the comics, Pepper and Tony don't have children (at least not yet).
The fact that the name Morgan was used in the movie for an entirely different Tony-related character does make you wonder. Especially because the seed for this child's name was planted ahead of time. At the beginning of Avengers: Infinity War, Tony and Pepper have a conversation about a dream Tony had in which Pepper was pregnant with a boy, who they were going to name Morgan after her "eccentric uncle." We don't know who this eccentric uncle is, so it seems like a throwaway line... until Endgame, where we find out that they did have a baby and went with the name Morgan.
It could be that this is just an Easter egg for fans of the comics, who remember there being another Morgan Stark, and for fans of Infinity War who remember Pepper and Tony's conversation. And that does seem likely, because Morgan doesn't do a ton in this movie besides be cute (she loves him 3,000!) and let Tony be a loving father. It doesn't seem like she's going to become Iron Man herself anytime soon.
But, as noted by Cinema Blend before Endgame came out, Katherine Langford was reportedly cast in the movie and some fans thought she'd be playing an older version of Pepper and Tony's child. One piece of evidence was that Langford posted a photo of herself with some Pepper Potts-y red hair. But, the actor didn't end up being in the movie at all, so either this was wrong or the story changed course. (It's also very possible that Langford is playing someone else, like a young Black Widow in a standalone movie, perhaps?)
Regardless of what was going on with Langford and why we got such an early reference to the name Morgan, it seems unlikely that this Morgan will become a superhero herself — at least not anytime soon. Marvel has a lot planned out already and that probably doesn't include a new Iron Man or Iron Girl or Iron Morgan — yet. This Morgan seemed to be more about showing the nurturing side of Tony, the one who had a somewhat normal life with Pepper Potts. You know, before that sad, but necessary and inevitable thing happened...