A six-year-old Queensland boy who donated his bone marrow to help keep his sick little brother alive for another 44 days has been recognised for his efforts with a trip to see a star dedicated in his brother's honour.

Isaac McWilliam, from Rockhampton, was three years old when his brother Ethan was born with a rare genetic condition, Shwachman-Diamond Syndrome.

His mother Michaela said the family spent a lot of time in hospital, and Ethan became more ill.

"As he got older he developed a condition called aplastic anemia, so that meant that his bone marrow didn't work, and as a result Isaac donated his bone marrow to his brother," she said.

"We were very lucky that he was a match, because both his father and I weren't, and so Isaac went to hospital – he was our superhero – and he donated his bone marrow to his brother."

Michaela McWilliam and other family and friends gathered to surprise Isaac. (TODAY Show)

Mrs McWilliam said she and her husband were eternally thankful to Isaac for helping to give them more time with their younger son.

"Unfortunately though, Ethan passed away two-and-a-half years ago… from other complications," she said.

"Isaac's bravery bought us an extra 44 days with our little man, so for that we're forever grateful and he is our hero for that."

Mrs McWilliam said a memorial star helps the family to remember Ethan.

"My mother's group… were generous enough to purchase a star in Ethan's honour from the Sydney Observatory, so Ethan now has a star somewhere up there in the sky but we've never seen it," she said.

When she learned of the TODAY Show's Australia's Little Heroes special, which recognises courageous and selfless children, Mrs McWilliam didn't hesitate to nominate Isaac.

This morning, TODAY Show weather presenter Stevie Jacobs surprised Isaac in Rockhampton, and gifted him a holiday to Sydney to view his brother's memorial star and visit Taronga Zoo.

Isaac McWilliam was named as one of the TODAY Show's Australia's Little Heroes. (TODAY Show)

"You are our little hero today, and we think you are just amazing, so congratulations and thanks to you," Jacobs said.

Isaac was also given money to spend on his favourite hobbies, including crafts and dressing up as superheroes.

Mrs McWilliam said Isaac dressed up as Iron Man to leave the hospital after donating his bone marrow.

"He's very into superheroes and Star Wars," she said.

Isaac told Jacobs that he also loved crafts and the outdoors.