Andrew Ridgeley revealed Wham! had to end as the group were about the "vitality of youth".
The group, which consisted of George Michael and Andrew, became one of the most successful pop acts of the 80s and sold more than 30 million records between 1982 and 1986.
George and Andrew were only 18 when the group was formed.
In a recent interview, Andrew, now 60, explained why the duo decided that the group couldn't continue into their adult years.
"As we achieved our goals, we came to understand that Wham! was about the exuberance and vitality of youth, and it couldn’t really develop into adulthood," he said.
George Michael Freedom music video star Tatjana Patitz dies at age 56"Wham! couldn’t age. When he asked me to consent to him releasing Careless Whisper as a solo record [everywhere except the U.S.], we knew that was the first step on his solo path."
He added to Los Angeles Times: "He talked for some time about doing a third Wham! album. But I think he understood that we’d just be going over the same ground."
Wham! released two albums and landed six number-one hits in the UK and seven consecutive top 10 singles in the US.
Earlier this month, Andrew told how George's death left a "void" in his life.
He became close friends with George – who he affectionately called "Yog" – when they met at school aged 12.
The star was in "disbelief" when he was told the music icon had died on Christmas Day 2016.
He said: "When I found out [George had died] it was a moment of disbelief.
"I think that's a very good way of putting it. I think anyone finds it difficult to comprehend when someone they’re so close to passes away, it’s an inconceivable moment. It leaves a void in your life.
"I’d love to just sit and have a sit-down lunch again, to chat and play Scrabble with Yog again."
Andrew also admitted he wished he worked harder despite Wham!'s global success.
George Michael superfan tears apart singer's £19m mansion with renovation workHe said: "What would I have done differently? I would certainly have worked harder, but I'm really not one for what-ifs."