The former JLS singer announced the news on Twitter by posting an image of himself beside his girlfriend Aimee Jade Azari, who posed in her underwear, showing off a large baby bump.
His former bandmates congratulated the singer, with Marvin Humes writing: "Huge congrats to @Oritse and @AJAzari the Williams baby is on the way!!! Very excited for you both! Big love (sic)."
JB Gill, who is also expecting a baby with wife Chloe Tangney, wrote: "Many Congratulations @Oritse @AJAzari wonder whether our lil one @ChloeSGill will have a boy or a girl to play with (sic)!"