Many thanks, Sandra and Eileen, for your replies.
Sandra, I will indeed contact the London Public Library to see if they have an obituary for Thomas Henry Brock. Yes, given Margaret's age when she divorced, it's possible that she remarried but I've exhausted all the Canadian marriage records on Ancestry without finding anything definitive. I assumed that, if she did remarry, it would have been as Margaret Brock because the maiden surname of the bride isn't required on Ontario marriage certificates (merely the maiden surnames of the bride's and bridegroom's mothers). Is that correct?
I do have that memorial for Sarah McLaren and her daughter, Mary Ann McLaren (later MacLaren in Canada). Marjory McLaren abandoned her husband, John Paterson, and daughter, Margaret, in 1921 when she travelled to Larchmont, New York, to take up a position as a domestic. Presumably, Margaret remained with her father and paternal grandmother, Jessie Paterson, in Cedar Street, Glasgow. Jessie Paterson died in 1926, at which time Margaret, age 13, went to Canada with her maternal grandmother, Sarah McLaren, and her first cousin, William McLaren, age 15, to live with Mary Ann McLaren who had emigrated there in 1921. Margaret's father, John Paterson, died at the age of 42 in 1929 in Glasgow. Rather sad story, it seems.
Yikes, Eileen! Motor manslaughter for a hit and run accident? In what newspaper did that article appear?
Thanks again to both of you.
All the best,
Rodeo