John Cowan of Ontario and Montreal

I need help in finding information about the parents and siblings of John Cowan (my great great grandfather). He is said to have been born in 1827 in Ontario or, possibly, Ireland. His parents were born in Ireland according to Canadian census records for John. In 1855 John was living in East Hawkesbury, Ontario when he married Annie Rutherford (daughter of William Rutherford and Catherine Craig) in Oxford Township, Grenville County, Ontario. Both John and Annie were Wesleyan Methodists. I cannot find the family on the 1861 census but from 1871 to 1901 they were in Montreal where John ended up owning and managing the John Cowan Chemical Company. John died in 1904, Annie in 1910.  Both are buried in Mount Royal Cemetery. Their only child (Lizzie Catherine Craig Cowan) was born in East Hawkesbury in 1857 and baptized in Hawkesbury. Lizzie married Richard Lister Gaunt in 1881.  They had one child (Reginald Tait Gaunt, who married Gertrude Isabel Haselden)  and lived in Montreal for the rest of their lives. 

I shall be grateful if anyone can help me find my John Cowan's family of origin.