Tributes are flowing for the son of Australian Rugby Union CEO Phil Waugh who died suddenly last week.

Jack Waugh was just 21-years-old when he passed away unexpectantly on Friday, September 11.

It is believed he passed away after an overdose.

The Waugh family issued a statement expressing their “profound sadness” at the loss of their “beloved” son.

“Jack was a fun-loving young man whose warmth and spirit touched all who knew him, and he will remain forever in our hearts,” the statement said.

“As we come to terms with the shock of his passing, we kindly ask that the privacy of his family and friends be respected during this time of grief.

“We are deeply grateful for the messages of love and support we have received.”

Jack was the eldest son of former Wallaby Waugh and ex-wife Michelle.

The former couple share a younger son, Charlie, who took to social media to pay tribute to his elder brother.

“To my big Brother, I love you more than words could ever explain,” he began.

“You helped me grow into the person I am today, always looked out for me and protected me when I needed it most.

“I’ll carry everything you taught me for the rest of my life.”