It has been a decade since his younger brother Timothy Wallis (26) vanished.
He was last seen in Dunedin in August 2010. After six years and no sightings, he was declared dead by the coroner in 2016.
He has never been located, and his cause of death remains unknown.
After a decade of pain, all his family wanted was closure, Mr Lees said.
"Ten years is a long time.
"We’ve suffered for years and years trying to find him — it’s the not knowing that’s the hardest part."
A missing person’s report was filed in 2015 after he was unable to contact his brother about a death in the family, Mr Lees said.
A subsequent police investigation was unsuccessful.
"I honestly don’t know what happened. We never got any information about it.
"He did have some [mental health] stuff going on ... He was quite transient — he moved around a lot. He loved hitch-hiking across the country but you could always eventually find him."
After the birth of Mr Lees’ son in Christchurch in 2008, Mr Wallis visited. It was the last time Mr Lees saw his brother.
His brother was a fun-loving, generous man who was always up for an adventure, he said.
"We grew up in different homes but as we grew up we saw each other more often."
Mr Wallis had two sons, a 10-year-old and an 18-year-old. They both had questions about what happened to their father, he said.
"Timmy’s got two kids who just want to know where their dad is or what happened ... His last photo was taken with his son, who was born a few weeks before he went missing.
"Christmas isn’t the same wondering where he is."
The family still celebrated his birthday each February.
Mr Lees said he struggled to live with regrets when it came to his brother.
"There was so much we needed to talk about and I’ll never get to say those things.
"The pain never really goes away. We all just feel so powerless."
A police investigation in 2015 was unable to find evidence he was alive, and the case was referred to the coroner.
A coroner’s report released in 2016 ruled based on evidence the 26-year-old had died, but the cause of his death remained unknown.
It said he was last seen on August 6, 2010, did not have a passport and despite having a transient lifestyle, had not been in touch with people who had expected to hear from him since then.
Mr Wallis had several distinctive tattoos, including a pentagram on the back of his left hand, graffiti-style writing on his neck and a tiger on his right cheek.
Mr Lees encouraged anyone with information to contact the police.
