An solo movie, Hawkeye is beloved by many MCU fans. However, arguably the most divisive aspect of Hawkeye's portrayal in the MCU is his secret family introduced in Joss Whedon's Avengers: Age of Ultron. In the film, the Avengers take refuge at Barton's farmhouse, where the superheroes meet his family: his wife Laura, sons Cooper and Nathaniel, and daughter Lila.
Hawkeye's family hasn't been seen since Age of Ultron, but they've been a key aspect of Clint's motivation throughout the subsequent movies. In Captain America: Civil War, Clint was called away from them for the conflict between Tony Stark (Robert Downey Jr.) and Steve Rogers (Chris Evans), for which he was eventually imprisoned in the Raft. While Avengers: Endgame trailer shows Clint happily enjoying time with his family, but the scene has fans speculating Marvel is teasing the arrival of Kate Bishop.
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Fans have long wanted Katherine Langford may play the fellow Hawkeye in Avengers: Endgame since the actress's actual role hasn't been confirmed yet. However, now speculation has turned to Lila Barton potentially being the MCU's Kate Bishop, but that would change quite a few things about the character as established by the Marvel comics. Introduced in 2005 as a member of the Young Avengers, Kate Bishop was created by writer Allan Heinberg and artist Jim Cheung as a legacy Hawkeye character - one who has no familial relationship to Clint Barton.
In fact, Kate gets the moniker of Hawkeye from Captain America in the Young Avengers comics, and only later meets Clint. Of course, Kate does train under Clint, and her relationship with the elder Hawkeye is portrayed as one of mentor/mentee in Matt Fraction and David Aja's Hawkeye run. However, Kate eventually breaks off from Clint in the Hawkeye comics and goes on her own adventure in L.A. There, fans learn that Kate comes from a well off family and her father is a villain who eventually puts out a hit on his daughter and Clint. That's a very different story than what fans think Avengers: Endgame is setting up.
Thanks to the comics, Kate Bishop has gained a dedicated fan following and it's understandable they would want to see the character introduced in the MCU. However, changing Kate's comic book backstory and tying it directly to Clint Barton is not only a cheap trick to get casual fans on board with the character, it also erases Kate's identity independent from Clint and ties her to the older Hawkeye unequivocally. Further, since Clint's daughter in the MCU is named Lila, Marvel Studios would even be changing Kate's full name in order to adapt the character. Of course, since Lila had such a minor role in Age of Ultron, it wouldn't be surprising for Marvel to retcon Clint's daughter's name to be Kate if they really were adapting Kate Bishop to the MCU in this way.
But the fact remains, the Avengers: Endgame trailer may not be setting up Clint's daughter as Kate Bishop. Certainly, Clint teaching her archery has tones of the mentor/mentee relationship between Clint and Kate in the Hawkeye comics, but that's not proof. And, considering how much Marvel would have to change Kate's character - which is inherently not tied to Clint and is arguably beloved because she's a hero independent to Clint, despite sharing the Hawkeye moniker - it would be better if that's not Kate Bishop in the Avengers: Endgame trailer.
