It wasn't until the Young Sheldon season 4 premiere, "Graduation," that it was revealed that they share a son. Since then, however, it sounds like they have expanded their family with more children. In Young Sheldon season 6, episode 19, "A New Weather Girl and Stay-At-Home Coddler," adult Sheldon's narration confirms his dad's theory that his kids would blame him when things go wrong in their lives. "Joke's on him, I did have kids and joke's on me, they say it all the time," Parsons' older character says.
When the couple's first child was revealed, it was clear that Sheldon named his kid after his best friend, Leonard Hofstadter, but also Leonard Nimoy from Star Trek. Both were incredibly important to him during the events of The Big Bang Theory.
It's curious when Young Sheldon will reveal the names of Sheldon's other kids, especially considering how thoughtful he and Amy were in naming their eldest.