'WILLIAM PRATT ([son of] Joseph) was born at Weymouth near 1670; mentioned in his father's will, 5 Mar. 1718-19, as a son. He married, near 1690, Experience King, daughter of Samuel and Experience (Phillips) King, born at Weymouth, 6 Oct. 1664.'
'PRATT, William (ca 1620-) & Experience [KING]; b 1692; Weymouth/Dorchester'
I assume a typo in his estimated birth year - probably should be 1670.