Cross in the post again, so I'll add this first:
Ottawa to Troy is actually overland -- Troy is in the far east of NY State, right up against Massachusetts, well away from Lake Ontario, and an odd place to go from either Toronto or the Ottawa area. When I have driven it myself, I've crossed the St Lawrence at Massena NY, then driven down the Lake Champlain waterway -- from Ottawa in the olden days, it could have been the Ottawa River to Montreal, and then down.
I actually would query whether that Ellen Lockhart in Troy had anything to do with Canada at all, just because Troy is such an odd place to end up. But apparently either she or James Crezie or both did have some connection with Toronto, from the other info you have.
Anyhow -- see below re Jane.

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From FS, 1861 Ontario census
Jane Young, 15/1846, Ramsay, Lanark, sheet 57, line 2
Stephen Young, 17/1844, same, line 1
Robert Young, 14/1848, same, line 3
I can't find any other Young of an age to be a parent on the same or preceding page. Have to look at Anc'y!
Can't find Henry Cavers in earlier censuses. He's a farmer in Ramsay in 1901, born in Ontario, with daughter Jennie E, Jr., 1880. Jeannie Cavers is the only birth showing to the couple in the index.
I also know the name Cavers in that neck of the woods.

(Someone with the same name as a person born c1850 in the censuses.)
1860
John Lockhart 67/1793, born Scotland; Ramsay, Lanark, sheet 67, line 11,
John Lockhart 31/1830, single, born Ontario ... line 12
(i.e. no wife on page; shown as widowed in 1871)
Jane Lockhart, 35/1826, single, born Ontario ... line 13
>> so this knocks out the Jane who married Robert Leach in NY as one of this family, since that Jane was born in Scotland, and more to the point, married in the US in 1853. Same year of birth though! Unless something dreadful happened between 1853 and 1860 and she went home (and somebody in NY state in 1850 just inferred from her accent that she was born in Scotland). I sure haven't been able to find Jane and Robert Leach in censuses in the US or Canada.
No other Lockharts in Ramsay in 1871.
1881
John Lockhart Jr is in Ramsay; no other Lockharts there.
Aha, the Cavers connection in Ramsay.
Thomas Cavers born c1849 married in 1874 -- mother Margaret Lockhart, father Thomas Cavers.
Henry Cavers 1846 must be another son of the couple. Yes, marriage to Jennie Young in 1878 shows parents as just Thomas and Margaret Cavers.
Margaret Cavers must be a daughter of John Lockhart who immigrated in 1821, and a sister of John Lockhart Jr 1830, who was uncle to Henry Cavers.
Margaret Lockhart and Thomas Cavers also had a child William Cavers who married Margaret Young in 1856 in Ramsay.
If you ever do need to find descendants of this Lockhart clan, you have lots of male Cavers to be getting on with.
1881
Margret Cavers, 56/1825, widowed, born Ontario, living in Beckwith, Lanark
fixed some typos