Who makes Kirkland hearing aids?

The current generation is manufactured by Signia (formerly known as Siemens).

Kirkland hearings aids are made by different hearing aid manufactures but labeled as Kirkland. In the early days meaning several years ago they were Rexton. Eventually GN Resound took over the brand and has been making them for Costco.

Sign a is the current manufacturer of Kirkland brand I believe. 

As others stated, Signea is the current manufacturer. Rexton had been used in the past as well. 

Unlike Signea or Rexton branded hearing instruments, the Kirkland branded aids are locked which means they can only be re-programmed and adjusted at a COSTCO facility.

Kirkland branded hearing aids are actually made by one of the major manufacturers who go through a bidding process against each other for the rights to build the Kirkland Signature package.  Typically Costco will go with the company willing to give them the best pricing on the package.  The package is just a specially priced bundled of product and service.  Currently they are made by Signia which is the new name for the old Siemens company.  Signia also builds the Rexton brand sold by Costco.  In previous years the Kirkland aids were built by GN Resound. 

The KS 8 model is actually manufactured by Rexton which is a sister company to Signia (Siemens).  If you goto Costco.com they have a lot of information on it under the hearing center tab.