This is not a family that I am researching but thought I might be able to find something for you.
Nova Scotia Vital Stats are available at www.novascotiagenealogy.ca
This is a free and searchable site.You may need todownload a free viewer program which is available onsite to see the actual record.I will just briefly outline what I found.You can check out the site and get all the details.You can also order copies of the records for a small fee.
All the following records are from the above site
Kathleen Harris died suddenly in Halifax of cardiac problems on November 23,1918.She was married and the informant was her husband F W. Harris (Book 25, page 17, #100)
Frederick Harris (it has been listed on the site as Frederick H-but the certificate clearly states Frederick W)died of protrate cancer May 27, 1925 at age 71.His parents are listed as Joseph Harris and Jane Harris both born England.His birthplace is given as Dartmouth and the informant is his daughter Estelle Harris.Reg Year 1925, Book 105, page 223).
In 1926 Estelle K Harris married J. George Muise in Halifax.She is listed as a spinster, teacher daughter of Fred W. Harris (Reg year 1926, Book 47, page 24)
In 1931 Estella Kathleen H. Muise died in Halifax of complications from amputation of her breast due to breast cancer.She is 35 and her husband John George Muise is the informant. (Reg Year 1931, Book 135, page 1231)
All the above is free online at the above site.If you have problems seeing the records, let me know.
I also could not find the family on the 1911 census.The names must have been mis-transcribed or something.I don't know if you have the 1871 Census with Fred W Harris living with his parents and siblings but I'll list it anyway
1871 Canadian Census District-Halifax East, subdistrict-Dartmouth (all the childern were born Nova Scotia Joseph Harris age 61, born England Jane Harris age 55, born England James Harris age 30 John Harris age 25 Mathilda Harris age 21 Frederick Harris age 17 also listed (same dwelling but separate household #) George Harris age 27 Annie Harris age 23
I checked the Vital Stat site and the marriage of George Harris, son of Joseph and Jane to Annie Isabel Wilson in 1870 is also listed there.