Charles O'Brien, 5th Viscount Clare (1673–1706) was the son of Daniel O'Brien, 3rd Viscount Clare and Philadelphia Lennard. He married Charlotte Bulkeley, daughter of Henry Bulkeley and Sophia Stuart, on 9 January 1696, at Saint-Germain-en-Laye, France. Henry Bulkeley was the "Master of the Household" for Kings Charles II and James II. Charles O'Brien and Charlotte Bulkeley had two children, Charles O'Brien, 6th Viscount Clare (27 Mar 1699 – 9 Sep 1761) and Henry O'Brien (b. 12 Feb 1701).