He is married to Mary Lucas.
They got married on May 31, 1752, he was 21 years old.Source 1
Child(ren):
A collection of family records: with biographical sketches bearing the name Douglas
Charles Henry James Douglas
Pg 147
96.
WILLIAM5 DOUGLAS (William4 Richard3, William2, William1), born in New London, Conn., Feb. 7, 1731-2. He married, May 31, 1752, Mary, daughter of Ivory and Mary Lucas, of New London. He was first constable and collector in New London from 1764 to 1772. He died Oct. 1, 1805. She died Jan. 31, 1810, aged 83 years. Children, born in New London :
242. i. William6, b. Sept. 29, 1753; m. Lucretia Caulkins.
ii. Margaret6, b. Feb. 19, 1755; m. Joseph Tinker, N. London.
iii. Mary6, b. Dec. 25, 1757; m. Stephen Morgan, N. London; set. Wethersfield.
243. iv. Caleb6, b. April 16, 1760; m. Grace Morgan.
244. v. Ivory6, b. 1761; m. Phebe Smith.
vi. Samuel6, b. abt. 1763; m. Deborah, dau. Samuel Morgan, N. London; d. s.p.
245. vii. Jonathan6, b. Aug. 31, 1765; m. Abigail Lay.
viii. Sarah6, b. 1767; d. young.
240. ix. Daniel6, b. 1770; m. 1st, Lucy6 Douglas, 2d, Amelia6 Douglas.
247. x. Josiah6, b. 1772; m. 1st, Mary Griswold, 2d, Mrs. Elizabeth (Starr) Bishop.
xi. Richard6, b. 1774; d. young.