June 22, 2015 5:15 AM EDT

The rumors were trueKanye West and Kim Kardashian West are expecting a son.

The reality star broke the baby boy news late Sunday on Instagram, sharing a photo of the rapper reading to 2-year-old daughter North for Father’s Day

“Precious moments like this when we were traveling on tour with you are what I live for,” Kardashian West, 34, captioned the photo. “You’re such a good daddy to North & you will be the best daddy to our new son too!”

Earlier in the day, she posted a sweet picture of West, 38, giving their little girl a kiss. “I’m so lucky to be married to a man who is so in love with his daughter, your bond is so irreplaceable,” she wrote. “Thank you for being such a good dad! We love and appreciate you so much! We’re so blessed to have you!”

After a struggle to conceive, the couple announced the pregnancy in May. The latest addition to the West family will arrive in December — and won’t be named South.

This article originally appeared on PEOPLE.com

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