Scott responded, "I love u mama/Wifey. We shall rage 4ever."
It's not the first time the couple have teased at having more kids. Last year, she posted a photo on Instagram of herself and Travis cuddling and wrote, "baby #2?" At the time, a source told Entertainment Tonight that the couple might try for another baby after he was done with his Astroworld tour, which ended in March.
"They want to have another child soon so it's close in age to Stormi, but they do not want to do this while he's busy on the road," the source said.
Jenner and Scott first celebrated his birthday last week with an Avengers screening party. Then, in the theatre, she had "husband" balloons for him and a cake that said "husband."
Earlier this month, Us Weekly did report that Scott and Jenner were in a really good place, even after rumours Jenner accused Scott of cheating made headlines in March. An insider told the publication that Jenner never planned on ending things with Scott. “Her and Travis are in a great place and she has no intention of breaking things off with him,” the source said.
WATCH: Kylie Jenner Celebrates Travis Scott's Birthday With An Avengers: End Game Theme.