Theo Albrecht, the billionaire who co-founded discounter Aldi with his brother Karl, has died.

The famously secretive German entrepreneur reportedly passed away on Saturday, aged 88.

Albrecht was understood to be Germany’s second-richest man, after his brother, worth an estimated €17bn (£14bn).

“Aldi mourns a person who was always decent with his business partners and employees and always treated them with respect,” the discounter said in a statement. “We are losing in him our highly respected founder and an upright person.”

“There are only a few people who have stamped their mark on an entire business sector of the economy,” said Stefan Genth of the German Retail Federation. “Theo Albrecht achieved just that.”

The Aldi retail empire was born in a small grocery store in the town of Essen owned by Albrecht’s parents. The chain last year notched up sales of €48.6bn and operates 4,000 outlets in Germany alone.