Willam Constable was probably born in Capel, Surrey in about 1588. A close study of the Constable family of Capel and Ockley, Surrey, (and eliminating all other possible candidates) shows that he was most likely the son of Nicholas Constable of Capel and an unknown mother, Nicholas' second wife. William married Susan Willett on 27th July 1612 in Newdigate, Surrey. Susan was born in 1590 in Newdigate, Surrey, the daughter of Edward Willett and his wife Faith. She was baptized on 20th July 1590 in Newdigate. The parish records for Capel do not begin until 1654 so there are no records to indicate how many children they had. Six of their children are named in the will of Susan's brother Nicholas Willett of 1636, Nicholas, William, Susan, Joan, Mary and Jane. William may have had 3 other children, John, Ann and Sarah but since they are not mentioned in Nicholas Willett's will, they may have been born later than 1636, however given Susan's age it's unlikely she had 3 further children so William may have married again. William is named in Nicholas Willett's will as his brother in law and and was made overseer. He was also a witness and overseer to the will of his brother John Constable of Ruggs in Capel, in 1638.

William Constable is shown on a 1662 map of Capel as holding land called Capel Church lands, held of the Manor of Dorking, lying opposite Capel church.