The World War II seaman will on Tuesday be awarded a posthumous Victoria Cross at Canberra's Government House.

Sheean's family have for decades fought for justice and put forward their case to several panels and inquiries.

His nephew Garry Ivory is among family members travelling from Tasmania, as well as Queensland, for the ceremony.

"I'll have two hankies in the pocket because I'm pretty sure there'll be tears," Mr Ivory told reporters at Launceston Airport.

"It's been a long time coming, but the feeling has made it all worthwhile. I had my doubts but I was never going to give up."

Sheean, 18, died in 1942 when the HMAS Armidale was sunk by Japanese bombers in the Timor Sea.

He strapped himself to an anti-aircraft gun, fired at enemy planes as the ship went down and is credited with saving the lives of 49 crewmates.

The Queen in August agreed to award Sheean the Victoria Cross following a recommendation by Prime Minister Scott Morrison.

An expert panel in July found an earlier decision to deny Sheean the award was wrong, with Mr Morrison describing it as a "substantial injustice".

Sheean, born in Tasmania as the youngest of 14 children, will be the first member of the Royal Australian Navy to receive the award.

His final act is the subject of a Dale Marsh painting which hangs in the Australian War Memorial.

"I would look at a copy of the painting - that used to inspire me," Mr Ivory said.

"He fought to his last breath, so I can do the same."

The Last Post will be played at Tuesday's ceremony before Sheean's medal is put on display at the War Memorial's Hall of Valour on Wednesday.

Sheean's Victoria Cross will be the 101st awarded to an Australian.

"He's symbolic of all our veterans, past, current and future," said Tasmanian Minister for Veterans' Affairs Guy Barnett, who has campaigned extensively for Sheean.

HMAS Sheean, a Collins Class submarine, is the first and only Royal Australian Navy ship to bear the name of an ordinary seaman.

Australian Associated Press