Josh Allen and Hailee Steinfeld's romance is starting to feel real serious ... as the two couldn't have looked more in love during a cameo they recently did for a baby's gender reveal.
The video was posted on TikTok on Sunday ... and in it, several family members and friends -- including Allen and Steinfeld -- appeared on screen to guess the gender of Allen's sister's unborn child.
After introducing themselves, Allen and Steinfeld both predicted it'd be a boy -- but check out the footage, the two looked super smitten with one another.