O'Brien, David J. of Lexington, Aug. 23, 2016, age 67. Loving son of the late Edward J. O'Brien and Bernice F. O'Brien (Doherty). Beloved father of Maureen P. O'Brien and longtime companion Chad Cunningham of Key West, FL, Deborah J. Crowell of Gulfport, FL., Michael K. O'Brien and his wife Kathryn of Bedford, Connor T. O'Brien and Colleen G. O'Brien of Lexington, the late David J. O'Brien Jr. and Eamonn O'Brien, and step father of Nicole L. Taylor of Rindge, NH. Dear brother of Elaine O'Brien of Beverly, Richard O'Brien and his wife Janet of Dracut, Jean Murby and her husband Gus of Medfield, and the late Edward O'Brien Jr. and surviving wife Anne of Woburn. Beloved grandfather of Flannery, Aine, Keaghan, Victoria, Jack, Alec and Colin. David is also survived by dear friends John Stewart and Lisa Perry, and by many loved aunts, cousins, nieces and nephews. David was a graduate of Lexington High School, class of 1966 and of Wentworth Institute, class of 1968; David was an accomplished General Contractor. Funeral from the Douglass Funeral Home, 51 Worthen Rd. Lexington on Monday Aug. 29 at 9am followed by a Mass of Christian burial at St. Brigid Church, Lexington at 10am with interment to follow at Westview Cemetery, Lexington. Relatives and friends are kindly invited to attend. Visiting hours Sunday from 3pm to 7pm.