Hsu Sho-er, 84, and her husband Chang Wan-ji, 83, have been operating a laundry in the Houli district of Taiwan for the past 70 years.
After their grandson, Reef Chang, noticed a number of clothes were being left behind he decided to set up an Instagram account, using his grandparents as models.
He said he originally set out to help alleviate his grandparents’ boredom, rather than make them famous.
Mr Chang told the PA news agency: “I wanted to let everyone know that they must remember to pick up their clothes or help them find a new owner.
“Besides, the life of a grandparent is very boring. I couldn’t bare to see them sitting in a daze every day.”
He said his grandparents agreed to set up the account “but didn’t think anyone would like it”.
However, WantShowAsYoung quickly went viral and they now have more than 388,000 followers from around the world.
They model clothes left behind, including a tartan skirt, purple raincoat and matching beige suits.
Mr Chang said: “Their favourite is when they have clothes matching their own old clothes, their eyes seem to glow, it’s as if they have returned to the same year.
“They feel that they have done a good thing because it tells elderly people not to limit themselves.”
The couple have donated some clothing to charities, but have still been left with hundreds of items.