Didn't find a William but did find a Henry. From The Kingston Chronicle: Saturday, January 9, 1830 Birth: "On the 5th inst., the Lady of Henry Cassiday Jr. Esq, Barrister at Law, of a son."
and
from The Kingston Chronicle: Saturday December 10, 1831, birth "On Saturday last, The Lady of H. Cassady, Jr., Esq. of a son." (Note the different spelling of the last name but sure it is the same Lady)

Hope this helps in some way.