A mother recorded the sweet moment her deaf son mouthed "hi" when meeting his baby sister for the first time."

Mackenzie Molina, 29, and her husband Joey Molina, 31, didn't realize their son Judah had lost his hearing when they filmed the heartwarming video.

In the video Mackenzie can be heard encouraging Judah to "say hi to your sister" and to the family's surprise, he responded with "hi."

But it wasn't until later they realized Judah had been reading his mum's lips.

Mackenzie, is a special events coordinator in Orange County, California, said: "I filmed this video a year and half ago when I didn't know my son was profoundly deaf."

"We thought he could hear us, but looking back now, it's clear he was reading our lips the whole time."

"It was shocking because we hadn't heard him talk before that other than babbling."

"Saying hi to his little sister were his first words and it's special in it's own way."

Judah, now three, initially passed his newborn hearing test.

But the couple later learned he had lost his hearing due to Cytomegalovirus (CMV), a virus Mackenzie unknowingly had while pregnant.

CMV can cause progressive hearing loss in infants, which was the case for Judah.

Mackenzie said : "Judah had CMV when he was born, but we didn't know it."

"I was asymptomatic and it wasn't until he turned two that we discovered he was fully deaf."

"He had passed his newborn screening so we had no idea."

The family struggled to get answers during the pandemic, waiting eight months to see specialists at UCLA, where Judah underwent a sedated hearing test that confirmed he had zero brain response to sound.

Mackenzie said: "Looking back, the signs were there. He wasn't responding to his name or startling at loud noises."

"It was when Joey banged a pot and pan next to his crib and he didn't wake up that we realised something was wrong."

Judah is a "kind-hearted" and "intuitive" child, particularly toward his two-year-old"

little sister Jovi.

Mackenzie said: "He's so protective of her and they're best friends."

"I like to call them twins because they almost do everything together."

"Even though they fight sometimes because they are just 17 months apart, he loves her completely."

The family also has two older daughters, Selah, seven, and Rio, six, and Mackenzie says Judah's bond with Jovi is especially close.

She said: "He loves her with his eyes."

"He's always watching her, making sure she's okay."