Andrew discovered George had a beautiful voice and told him he should pursue a career in singing. George was quite shy at the time, but felt more confident paired with Andrew. The two joined a ska band called The Executive with some other musician friends.
By the time The Executive ended, George was much more used to performing and was less shy than he had been. George and Andrew decided to give it a go and formed a new group (that would be Wham!) with Shirlie Holliman and Dee C. Lee as backing singers/dancers. In 1982, Dee C. Lee exited and was replaced by Pepsi DeMacque. Wham! is largely considered a duo, but I think the ladies deserve a bit more credit than they normally receive.
When their first album, Fantastic was released in the U.S. in 1982, the group was called Wham! UK, due to a band in the U.S. already using the name Wham. Eventually, the other band stopped using the name and the "UK" part was dropped by the time Make it Big was released in 1984.
Non-fans: you're saying, "Oh yeah! Them!" right now, aren't you? ;)
With the 1986 release of The Final (an alternate version, Music From the Edge of Heaven came out in the U.S.), Wham! disbanded in what has been called the most amicable band breakup in history. Andrew knew George was ready for a solo career, so he moved on and let him do the same.
Many call Andrew "the other guy" in Wham!, due to the enormous success of George Michael's solo ventures. However, George credits Andrew with helping him come out of his shell. It was also Andrew who had the drive and determination to make Wham! (and George) famous. And he succeeded.
George Michael has arguably one of the best voices in the history of recorded music, but there wouldn't have been a Wham!, or really, a George Michael, without Andrew Ridgeley.
Andrew released an album, Son of Albert, basically just because he had to (per Wham!'s recording contract). He then settled in Cornwall (U.K.) to live out a private and domestic life with Keren Woodward, a member of the group Bananarama. Andrew surfaces with a new interview every now and again. He also does quite a bit of work with environmental organizations.
The ladies of Wham! became a group called (fittingly enough) Pepsi & Shirlie. They initially split in 1991, but made a comeback in 2011 and are still performing now.
Deon Estus, the bass player for Wham!, also released music, the biggest hit being Heaven Help Me, featuring guest vocals by George Michael.
Many facts gleaned from Wham!'s Wiki.
Videos embedded from YouTube.