But if you weren't paying close attention, you might've missed the announcement.
"Precious moments like this when we were traveling on tour with you are what I live for," Kardashian captioned a photo of Kanye and daughter North West, going on to subtly drop the second baby's sex. "You're such a good daddy to North & you will be the best daddy to our new son too!"
In the photo, Kanye sits with Nori, playing with a storybook. The adorable photo is just one of the many tributes Kim put online for his Father's Day.
Kimye announced they were expecting a second child at the end of May on "Keeping Up With The Kardashians," and while there has since been lots of speculation, Kim has been quiet about sex. However, she wasn't afraid to speak up when rumors of twins started flying, quickly shutting down any talk of two new babies or having to use a surrogate.
The new West boy will be little brother to North, who turned 2 years old on June 15. She was born a day before Father's Day in 2013.