Yes it's complicated because John came from Canada and did not stay long enough in Minnesota to "show up" in records, and then moved to Texas. He first married Frances Breaders (per the death certificate for Sadie that you have), then he next married Nancy Broaddus (per Henry's death certificate), then he next married Sarah Gray, a widow whose married name had been Crisp. John died before 1917; Sarah died in 1917 (her death certificate says she is a widow).
No one has yet found John, Sarah and family in the 1910 census.
I'm summarizing above to show the big difference it makes whether Sadie's death certificate clearly says her mother's name is Breaders. If the handwriting is hard to read, is it possible it says Broaddus? Can you get a copy of Henry's death certificate to compare the names Breaders and Broaddfus? As it stands now, I would guess it's two different women.
Here is an obituary for Libby Morris Senesac. She is the wife of Nolan Senesac, who is Henry's son and also Sadie's nephew.http://www.tricountyleader.com/news/2007-06-07/obits/011.htm...
Congratulations on finding out so much about this family.
I haven't found an immigration record for John Senasac and family circa 1855, but it looks like the surname is spelled Sénésac (and variations) in French Canada.