The couple already have daughter Stormi, 14 months, together, but in an Instagram post uploaded in celebration of Travis' 27th birthday on Tuesday, Kylie revealed she's keen to make them a family of four.
Kylie said she wants to "f**k around and have another baby" with the 'Sicko Mode' hitmaker, whilst also referring to him as her "hubby" - which is short for husband - despite the pair not being married.
Sharing several snaps of the pair together, including some which featured baby Stormi, Kylie wrote: watching you evolve into the partner, friend, son, and father you are today has been so fulfilling. my real life bestie & hubby all wrapped into one. i love you and I'm so so proud of you. happy happy birthday. let's f**k around and have another baby."
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watching you evolve into the partner, friend, son, and father you are today has been so fulfilling ♥️ my real life bestie & hubby all wrapped into one. i love you and I’m so so proud of you. happy happy birthday 🎉🎁 let’s fuck around and have another baby. 🤪
A post shared by Kylie (@kyliejenner) on
The sweet tribute comes after the 'Keeping Up with the Kardashians' star had a billboard installed to celebrate Travis' birthday on one of the busiest intersections in West Hollywood, between Santa Monica and La Cienega.
On the billboard, 21-year-old Kylie wrote: "Happy Birthday Daddy. Love, Mommy & Stormi XO. (sic)"
Meanwhile, Travis had previously revealed how he'd like to get married to Kylie "soon" but he wanted to "propose in a fire way" first.
He shared: "We was just two kids, f***ing around. Maybe, like, the first week, you don't know if it's real or a fling. Then the second week you're like, 'Whoa, I'm still talking to her, she's responding, I'm responding. We ain't run out of a thing to say.' And it got to a point where I was like, 'I need her with me to operate. She's that one.' We'll get married soon. I just gotta sturdy up - I gotta propose in a fire way."