The first Westbrooks to arrive in North America were John's great great grandparents:
Jan Teunissen Van Westbroeck 1592 Netherlands - 1665 New York USA
Eyglye Cornelise Bosch Theunise 1594 Netherlands - 1675 New York USA
"Jan Teunissen, the first sheriff of Brooklyn, (now New York), was from the village of Westbroek in Holland. He was appointed sheriff in 1646 by Gov. Kieft and was the son of Teunis Ryersen."
New York State Library Historical Bulletin #10, Vol 3, Notorial Papers 1& 2r 1660-1696 (U. of N.Y.,1918), pp140-141.
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Brothers: Haggai Westbrook / Thomas Ridley Westbrook / Captain Andrew Westbrook

Mother: Sarah Decker 1739 New York, USA - Ontario Canada.

Father: Anthony Westbrook 2 Sept 1738 Kingston, New York USA - 1793 Ontario Canada
Anthony was a Loyalist during the American Revolution. He fought under Brandt in 1777, was captured and held prisoner for 21 months. Anthony Westbrook was a member of Joseph Brants war party July 29, 1779.
(Public Papers cf George Clinton, Vol. V, 1901, p. 163.)

He appears with his family as a Loyalist on the Return of Persons at Niagara, 1793. (Haldimand Papers, Vol. 105, P. 395a, in the Public Archives of Canada, Ottawa, Ontario.)

Minutes of the Executive Council of Upper Canada Friday, 29 June 1793
John Westbrook and Anthony Westbrook: Memorial that having made the settlement on which they live adjoining the west line of Township No. 8, near the road laid out from the head of Lake Ontario to the river La Tranche, that they were encouraged by the Land Board to settle upon those lands four years before they were surveyed, which proves now to be reserved lands, your petitioners pray that the land may be confirmed to them. Ordered that they be confirmed in the possession of their lands and that the Surveyor be directed to make reserves for the Crown in some other part of the Township.

At the Council Chamber, Navy Hall 13 July 1793
Anthony Westbrook: Petition to take up land between Long Point and Turkey Point on the west side of Lake Erie. (N.B. Anthony Westbrook has taken up his land at the same place in August last)