Hello
I am not related but

Have you used the site (it is free) www.familysearch.org? They have a NEW site but you still can get into the old one.
If you look at the marriage licenses you will find a lot of the family marriage licenses including Jelle(Charles) Kooistra & Carrie DeBoer married in Conrad MT, married 1913.

Also from that family Dena married 1934, both Agnes's marriages 1934 & 1944, Helen married 1939. and Edna married 1944.

The Mink family they show Mary married 1929 and John W married 1944.
The census that the site showes said that they lived at Midway Montana. Midway was a town that was half way between Brady and Conrad. It is just farm land now. No town.

You can call the Pondera cemetery - Hillside Cemetery -their phone is 1 406 289 0586, to see if any of your family is buried there. There is only one funeral home in Conrad for the area - Pondera Funeral home - 302 South Main - Conrad MT 59425 - phone 1 406 278 3333. They should know if there was a cemetery at Midway or not. They could check there records to see if they did the services

The Montana State Genealogy Society has a Montana State death index.. It has the following people ans dates.

Louis Mink D.D March 29 1956 Pondera County
Jeannie K Mink D. D. November 1 1945 Pondera County
John W Mink D. D. December 31 1996 Pondera County
Lois Mink D. D. April 8 1956 Pondera County

Charles Kooistra D. D, July 17 1925 Pondera County
Leigje Kooistra D. D. August 14 1945 Pondera County I didn't see this name on and census so possibly first name is wrong.

John Kooistra D. D. April 27 1967 Ravalli County
William Kooista D. D. March 7 1936 Pondera County

Anna DeBoer D D January 1 1982 Gallatin County
Douglas DeBoer D. D. June 15 1992 Gallatin County
Shirley DeBoer D. D. June 7 1992 Gallation County
Victor DeBoer D. D. December 3 1994 Yellowstone County
Edward DeBoer D. D. September 29 1997 Lewis & Clark Co Charles DeBoer D. D. March 9 1958 Gallatin County
Albert DeBoer D. D. June 9 1917 couldn't read code for county they died in
Marguerite W DeBoer D. D. October 16 1923 Gallatin County
Infant DeBoer D. D. January 1945 Pondera County
father is Thomas DeBoer
Dick DeBoer D. D. October 15 1947 Gallatin County
George DeBoer Georeg D. D. November 6 1953 Daniels County
Caroline DeBoer D. D. June 9 1966 Lewis & Clalrk Co.
John DeBoer D. D. July 1 1967 Gallatin County
Grace DeBoer D. D. January 16 `973 Pondera County
Thomas DeBoer D. D. September 5 1974 Teton County
Lucy DeBoer D. D. November 24 1970 gallatin County

George Mink D. D. October 16 1918 can't read code for name of county they died in
Lillian Mink D. D. March 1 1919 Yellowstone County

Conrad has a weekly newspaper that does carry obits
The Independent Observer #7 3rd Avenue SE Conrad 59425 phone 1 406 271 5561 or you can re-post for obituaries - of the people you are related to - on Cascadr County because the Great Falls Tribune is the main newspaper for this part of Montana. For copies of the death certificates go on the Pondera County website go to the Clerk & recorder Office and print the form to order the certificates. Copies of the Marriages licenses can be obtained from the Cleerk & recorder. You can get their info from there website.
Good luck
Linda