Lillian Snook
Lillian Snook (about 1903 - ??) was a possible daughter of George Snook and his wife Anna Parsons.
Summary of evidence
1. She appears with the family as the daughter and an 18-year-old tailoress in the 1921 census, but strangely not in the 1911 census, when it's just George, Annie, their namesake children, and George Sr.'s brother Edward Langley Snook living together.
2. Another possible reference to her is in George Jr.'s obituary, which mentions his being survived by a sister, "Mrs. Don McLeod" of Fort William.
3. In George's 1930 obituary there is no mention of her! She is not listed as a surviving child, or at all.
4. Other possible references to her are a Mrs. Lillian McLeod living at 290 Argyle Street on two voters' lists in 1935 and 1949, as a widow, with Mr. and Mrs. Lorne McLeod, the Mr. being a truck driver in 1935 and a fireman in 1949. (possibly her brother-in-law).
5. At the wedding of her mother's brother Joseph Parsons in Port Arthur on 20 April 1911, a "Miss Lillian Snook" is cited as accompanying the bride:
"The bride... was attended by Miss Lillian Snook, who wore a dress of negre brown trimmed with cream point lace and beads, with a corsage bouquet of pink carnations"
— Port Arthur News-Chronicle, April 1911
A search of the Chronicle-Journal archives might find an obituary or marriage reference.