Jamie Fraser’s father Brian („Brian Dubh“) is born as an illegitimate son of Simon Fraser, Lord Lovat, „The Old Fox“. His mother is Davina Porter, a maid in the Fraser of Lovat’s keep.
Brian dies before Outlander begins but is mentioned there several times.
In Written in My Own Heart’s Blood Roger and Brianna MacKenzie meet Brian when they inadvertently travel to the year 1739.