Saturday marks a milestone for I Love Lucy, the granddaddy of sitcoms: Lucy’s babies — Desi Arnaz Jr. and the TV character he inspired, Little Ricky Ricardo — turn 60.

A few months after the blessed events on Jan. 19, 1953, the first national issue of TV Guide featured a cover photo of Desi Jr., a small picture of his mom, Lucille Ball, and the headline, “Lucy’s $50,000,000 baby,” referring to the marketing value of the real and reel babies.

“They wanted to capitalize on Little Ricky and Desi’s births. In the public’s eye, Desi was Little Ricky and Little Ricky was Desi,” said former child actor Keith Thibodeaux, who played Lucy and Ricky Ricardo’s son from 1956 to 1960.

To this day, many fans mistakenly believe Desi Jr. played Little Ricky. He never did.

“For his entire life, Desi Jr. has been driven crazy by people saying ‘I loved you on I Love Lucy,’” said Gregg Oppenheimer, son of series creator, producer and head writer Jess Oppenheimer.

Nearly every television viewer in America (98.6 percent) was tuned to I Love Lucy the night Lucy Ricardo gave birth to Little Rick. The episode aired hours after Ball delivered her real-life son, said Oppenheimer, who recently released an audio book based on his father’s memoir, I Love Lucy: The Untold Story.

Fifteen million households were watching, Oppenheimer said. “And you can bet everyone in the neighborhood who didn’t have a TV came over for viewing parties.”

Lucy premiered Oct. 15, 1951, three months after the birth of the couple’s daughter, Lucie Arnaz. By the end of season one, Ball and husband/co-star Desi Arnaz knew they were going to have a second child.

CBS and the show’s sponsors initially objected to art imitating life.

“Back then, you couldn’t say the word ‘pregnant,’ ” Oppenheimer said. “They referred to her as ‘expecting’ or ‘she’s going to have a baby.’ ”

That didn’t deter Oppenheimer’s father. “My dad’s reaction was, ‘This is wonderful. I was wondering what we were going to do in the second season.’ ”

Six young actors eventually played Little Ricky: newborn James John Ganzer, twin babies Richard and Ronald Simmons, twin toddlers Joseph and Michael Mayer and the boy most associated with the role, Thibodeaux.

“I was formed and fitted for that part,” the 62-year-old said in a telephone interview.

At age 3, Thibodeaux had been a drummer on bandleader Horace Heidt’s TV show, a talent he shared with Ricky Ricardo Sr. Later, his father heard I Love Lucy was looking to cast a 5-year-old Little Ricky.

“Lucy saw me and thought I was cute,” Thibodeaux recalled. “She said I was cute, but what can he do? My dad said, ‘He plays the drums.’ She said, ‘Oh, come on!’ ”

Thibodeaux demonstrated his drumming abilities and got the job. Desilu studio execs gave him the stage name Richard Keith, making him a real-life Little Ricky, as he was billed during The Lucy-Desi Comedy Hour years (1957-60).

Ball treated Thibodeaux as an adult cast member, but “when I was around there was no crude language, no off-color jokes,” he said.

“She was like a mother, literally like a mother. When I first came on the show, I called her Miss Arnaz, Miss Ball. She said, ‘No more Miss Ball, call me Lucy. Call him Desi.”