Do you have his obit? I found a copy of it at Newspaper Archives. Among his survivors, it listed his sisters Mrs. James Konop of Coleman, and Mrs. Joe Donias of Milwaukee.

Herald Times Reporter, June 4, 1973 Page 22
(Manitowoc-Two Rivers, Wisconsin)

Mrs. Mary (Anna) Schaffer Donais, 83, of Milwaukee, died Saturday night at St. Joseph Hospital, Milwaukee following a lingering illness.
Funeral services will be at 2 P.M. Tuesday at Urbanek and Schlei Funeral Home, Manitowoc. The Rev. Paul H. Blaufuss will officiate, and burial will be in Evergreen Cemetery, Manitowoc. Mrs. Donais, nee Teche, was born August 14, 1889 at Spruce, Wis., daughter of the late George and Mary Teche. She was married to Joseph Donais, March 28, 1935 at Crown Point, Indiana, residing at Milwaukee.
Survivors include a son, Harold Schaffer, of Manitowoc, three step-sons, Norman and Lawrence Donais of Milwaukee, and Gilbert Donais, California, a step-daughter, Mrs. Lynn Asnin of Florida, a sister, Mrs. Josephine Konop of Oconto Falls; four grandchildren and four great-grandchildren.
Friends may call at the funeral home at 11 A.M. until the hour of service.

There are multiple articles about the Teche family at www.newspaperarchive.com It is a subscription site, but you can search for free, and view two articles a day for free. I found an obit for Mary Teche (Mother) in 1926, but have already read my two pages for the day. I was able to see that her maiden name was Blazek, and she was survived by a brother John Blazek.