Thomas and Margaret had three children that I have found. Olive Lucy (b1875) became a nurse and worked at Rhode Island Hospital in Providence at least until 1940 when she was a house mother at the nurses' home. She crossed the border at Buffalo in 1941 and that's the last I have found. I assume she never married. There is also a Miss Olive L Niles in Toronto in the 1945 voters' list, so she may have lived there in retirement.
Thomas Marvin Niles (b 1887) married Jennie Wallce in Newmarket in 1912 and had a daughter Olive Elizabeth in 1913.
I'm pretty sure that William Cane Niles (b 1882)married Fidelia (Delia) Fillner about 1908 either in Minnesota or North Dakota. They had 3 children, William Margaret and Olive, but I think the marriage must have ended in divorce and William remarried to Anna T. He is a millwright at a packing house and emigrated in 1904. This coincides with a gravestone with the correct birth date in Westminster Memorial Park, Westminster, Orange County, California, and the California Death Index. Happy to help further if you are interested. I am trying to build the Cane family tree. I think Lucy Cane (Nathaniel's wife) is sister not only to William Cane of some renown in Newmarket, but also to my gggrandmother Margaret Cane, and also two others, James and Edward (though sometimes the spellings changed).