The rapper, 26 — who is dating Kardashian's younger sister Kylie Jenner — commented on Chyna's Instagram photo, which showed an emoji of the model pregnant.
"Congratulations," he wrote, also adding a carp streamer emoji. (Kardashian posted the same emoji that shows Chyna in a crop top while cradling her bare baby bump.)
This will be the second child for Chyna, 27, and the first for Kardashian, 29. Tyga and Chyna are parents to son King Cairo, 3.
"Everybody deserves 2 be happy. What some1 does for their happiness is not my concern, as long as it's not interfering wit my happiness," he tweeted. "It makes me happy to see the mother of my son happy. My only concern in this situation is my son. I want him in happy environments. He's innocent in this. & I want him to feel as much love as possible."
Chyna and 18-year-old Jenner, meanwhile, have butted heads in the past. Last month, they appeared to make up when they reunited for a photo-op. "When we’ve been best friends the whole time," the makeup maven captioned a photo of the two via Instagram on April 21. Kardashian reposted the pic, and added: "So happy my girls finally got to talk and make peace! #MyFamily #AllLove."
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