'Sheikh' is a honorific title given to new Muslims, or converts. Since during the last few generations, most conversion took place from Hindu business class, Sheikhs have come to be known as a business class in general. A good proportion of Punjabi business class is composed of Sheikh biradary.
I belong to Arain biradary, and my best friend is from Sheikh biradary. His great grand father converted to Islam around hundred years ago. His previous name was Madhava Mal. I do not know if this information is helpful to you. Take it as you wish.