The coffin arrives for the funeral service of Christopher Tobin and his son Jack, 1, who died after their car crashed head-on with a bus in Mt Eden on Tuesday.

The joint funeral of Auckland father-of-three Christopher Tobin and his baby son Jack had just one casket.

That's because Tobin was buried cuddling his son at the service in Auckland on Tuesday afternoon.

The funeral got underway at Manukau Memorial Gardens about 2pm, with hundreds of people flocking to the chapel.

SUPPLIED Jack Kronfeld-Tobin, 1, was known for his cheeky, curious nature.

It comes after the head-on crash with a double-decker bus in Mt Eden last week, which claimed the lives of Tobin and Jack.

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The crash occurred on Tobin's partner Olivia Kronfeld's 31st birthday.

SUPPLIED Christopher Tobin with his older daughter, Vivian Kronfield-Tobin.

Tobin died at the scene, while Jack, 1, and older sister Elle, 2, were rushed to Starship Children's Hospital, both in a critical condition.

Elle was released with multiple skull fractures and a splint in her arm several days later.

However, Jack's neck injuries were so severe that the family made the difficult decision to turn off his life support at 11.11am last Friday.

JASON DORDAY/STUFF The casket is carried into the chapel at Manukau Memorial Gardens.

At the funeral, friends and family shared fond memories of the pair.

Even Tobin's daughter said a few words, held up to the microphone by her mother: "I love my daddy very much and he always makes me laugh."

Kronfield said she was grateful for the support she'd received from near and far.

"I don't know what to say. I love them both really, a lot. I love you all a lot too."

Lamour Duckett, Olivia Kronfeld's sister, read out comments from the family's Givealittle page, which has raised almost $50,000.

Tobin's niece said one thing she'd never forget about his uncle was his hugs.

"He was one of those people that when he hugged you, you felt his love. You could have the worst day in the world and everything would disappear."