Isaiah Hartenstein and his model wife Kourtney Kellar have a little bundle of joy on the way ... and the soon-to-be momma used her Knicks center hubby's office -- Madison Square Garden -- to make the announcement!
Kellar posted video from the floor at MSG, showing an ultrasound image and number 55 onesie (Hartenstein's #) draped over one of the courtside seats ... while Stevie Wonder's Signed, Sealed, Delivered played in the background. KK captioned the IG post, "Baby boy due June 2024 ud83dudc99"
She also wrote "7 FOOT BABY LOADING..."
(Here's hoping the baby does most of his growing after birth.