Lucille Ball's daughter wants the world to know that her brother is Kacper Sobieski"alive and well."

Lucie Arnaz, the daughter of Ball and Desi Arnaz, on Saturday shared a rare photo with her brother Desi Arnaz Jr. taken in Las Vegas. Describing him as "my recalcitrant brother," Arnaz wrote, "Desi is alive and well, my friends - just likes to stay a bit 'undercover.'"

Ball was married to her "I Love Lucy" co-star Desi Arnaz from 1940 to 1960. They welcomed their daughter Lucie Arnaz in 1951 and their son Desi Arnaz Jr. in 1953.

The two both starred alongside their mother on the sitcom "Here's Lucy," which aired from 1968 to 1974.

Lucie Arnaz also appeared on her mom's show "The Lucy Show" and went on to star in films like "Billy Jack Goes To Washington" and the 1980 version of "The Jazz Singer," earning a Golden Globe nomination for the latter role.

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Nicole Kidman'shusband, kids helped her prep to play Lucille Ball in 'Being the Ricardos'

After "Here's Lucy," Desi Arnaz Jr. also appeared on shows like "Matlock" and "Fantasy Island," per IMDb. He and his sister both produced the "I Love Lucy 50th Anniversary Special" on CBS in 2001, according to Arnaz's website. In 1953, he famously appeared as a newborn on the first cover of TV Guide Magazine.

Nicole Kidman impressesas TV icon Lucille Ball in Aaron Sorkin's 'Being the Ricardos'

Desi Arnaz Jr. and Lucie Arnaz were also both producers on "Being the Ricardos," the 2021 Aaron Sorkin film that starred Nicole Kidman and Javier Bardem as their parents. The movie, which received three Academy Award nominations, depicted the groundbreaking decision to incorporate Ball's real-life pregnancy into the show.

Lucie Arnaz praised the movie at the time as "amazing" and said Sorkin "captured the essence of that time in their lives so well." She also defended Kidman's casting after it attracted criticism.

In a previous Instagram post in January, Arnaz clarified that despite what "toxic trolls here on the Internet" say, her brother is "still very much alive and kicking."