http://www.brucebarnard.com/roots/francis.pdf - there is a 'Sir Willard Bernard' b. 1867 on this family tree. He seems to be the son of Amos Fowler Bernard, this is probably the family in 1880:

Household:

Name Relation Marital Status Gender Race Age Birthplace Occupation Father's Birthplace Mother's Birthplace
Amas BARNARD Self M Male W 59 NY Farmer NY NY
Hellen E. BARNARD Wife M Female W 47 VT Keeping House VT VT
Bert BARNARD Son S Male W 19 MI NY VT
Fred J. BARNARD Son S Male W 15 MI NY VT
Willard BARNARD Son S Male W 13 MI NY VT
Hellen BARNARD Dau S Female W 12 MI NY VT
Charles BARNARD Son S Male W 4 MI NY VT
Clara GEYER Other S Female W 21 MI Servant GER GER
David BARNARD Brother S Male W 46 NY Works On Farm NY NY

Source Information:
Census Place Handy, Livingston, Michigan
Family History Library Film 1254592
NA Film Number T9-0592
Page Number 111B

I'd suggest trying to track down his obituary, that should tell you why he was called 'Sir'.