You surely had a great amount of help from the Canadian researchers who did a lot of digging back then on your behalf... cosmac, LindaGW, JaneyCanuck, Jacquie in Canada and I must apologize to them for any recent duplication on my part.
Have looked for Martin/Henry in 1891 but can't find him. Am also wondering, if he did arrive in 1887, he would have been just a young teen...Not finding them in 1881 makes me wonder if they were missed, or if a parent may have passed away & the family split up, either with relatives or institutions.
- also no sign of known siblings Annie Harriet Martha Robinson 1875 or Charles Wood Robinson 1876
All living (15) Cross St. when baptised St Mary, Preston, Lancs.
*Adding *found these in 1891!!! If site under construction - check again later

1891 census enum. april 20th Ontario Cardwell Sub-district Albion
Henry Robinson, 1871 Eng. domestic/farm helper ( made me think - homechild/farmBoy
https://recherche-collection-search.bac-lac.gc.ca/eng/Home/Record?app=census&IdNumber=25147729&ecopy=30953_148131-00795 However - Looking at forename as Grattan - there are TWO
Speculation:
Could these both be entries for same person??? 3 days apart? ...1891 census Ontario/Grenville South/Cardinal ( scroll to top of page 16)
taken April 13th - lodging at a hotel
says b. Eng. ( although says Rel: C.O.E) pretty sure it says Tel. operator (telegraph?)
http://central.bac-lac.gc.ca/.redirect?app=census&id=25408097&lang=eng&ecopy=30953_148139-00402taken April 13th - 1891 census /Ontario/Cornwall and Stormont/Osnabruck
- listed as a nephew of widower Francis Anderson whose family are all from Ireland
both of whom work for the Railway... Grattan 's entry says b. Ireland
http://central.bac-lac.gc.ca/.redirect?app=census&id=25200434&lang=eng&ecopy=30953_148133-00167Will be hard to determine which is the correct entry...Wonder if this fellow might know who to contact for some Rail/telegraph history as he's obviously a fan.
http://www.trainweb.org/telegraphgene/tgontario.htm