Gosh, they were a long-living family weren't they - so many of them well into 80's and 90's....
Loose end........tie up
John MacKENZIE's brother George didn't go to the US - he appears to have died between 1905 and 1912, possibly closer to 1911/12. By 1901 George had a new wife, indicating 1st wife Wilhelmina had died (or divorced but death more likely):
1901: Seaforth Lodge Ballifeary Rd - Inverness, Inverness-shire
Parish 98, Ed 12
Head: George MacKENZIE 41, Civil Service Asst Supt. Postal Teleg, b Inverness
Wife: Jane MacKENZIE 35, b England
Son: William Robert MacKENZIE 13, Scholar, b Inverness
Son: Allan Matthew MacKENZIE 11, b Inverness
Son: Randle MacKENZIE 1, b Inverness
In late 1912, his 2nd wife Jane was herself a widow and travelling to the US with her children and stepson Allan. They were going to Allan's older brother George Alex MacKENZIE already in New York. The ships manifest for that journey again brings Margaret, Mrs Andrew G SMITH, wife of a Railway Station Master in Glasgow, into the frame:
SS California - dep Glasgow 16 Nov 1912, arr NY 25 Nov 1912
Alan McKENZIE 23, single, Chemist
Jane McKENZIE 37, widow, Housewife
Randell McKENZIE 11 (female), Student
Ethel Beatrice McKENZIE 10, Student
Edward Horace McKENZIE 9, Student
Constance D McKENZIE 7, Student
Alfred D McKENZIE 11mths
All children, incl Allan, born Inverness
Jane born Liverpool, England
All, incl Jane say Nationality is Scotch
All last residence Inverness
Contact in UK: Aunt (of Allan and all other children), Sister in Law (of Jane):
Marg SMITH, Station House, Maxwell Park, Glasgow
All destined for : New York City.
Going to in US: Brother (of Allan and all other children), son (of Jane)
George Alex MaKENZIE , 480 Greenwich Str, New York
It's possible a year later, that Jane, widow Mrs G MacKENZIE, is living at 180 Crystal Road, Brooklyn - to where Allan goes, and later his sons go, in 1913 when they arrive in NY.
You mentioned "(From a biography of John Mackenzie in 'Moving Picture World' 9 Oct 1915, p.264") - Is that one on-line someplace - would love to read it!
If you don't have US Census for John etc, you could also put a lookup request on the US Boards for the 1920/1930 Census' - and perhaps a link back to this topic for reference.
Cheers
AMBLY