Hi, I have brothers William Drennan Thomas Hamilton Drennan and John Gallaway Drennan. Their father was William Lennox Drennan and their mother was Letitia Gallaway they married in co Down 1840. William's father was Dr William Drennan MA MD who married Sarah Swanwick in 1800 they had 7 children. William was the son of Rev Thomas Drennan. Rev. Thomas Drennan 1696-1768, married 1741 Ann Lennox 1719-1806, they had 9 children (6 died in childhood)Ann Lennox was the daughter of Robert Lennox and Martha Hamilton who were my 6th x great Grandparents. You can email if you wish and I will pass along what I have if these are your Drennans.