Buck is Dougal and Geilis Dunkin son that they secretly gave to another family who lost a baby and there last name was Mackenzie also bc they lived at Leoch and were part of the Mackenzie clan.and they raised him and he doesnt know yet but Roger will tell him who his real parents are. Claire told Roger about it when she showed him his family tree. So Buck is Jamies 1st cousin and Briannas second cousin He is also Hammish Mackenzies half brother. Jocasta is his aunt as well. Too bad he didn't know about all the family that could of helped them settle in the colonies. He appears to have Dougals famous temper (having Roger hung for having a hot eye for his wife!😂) So Jemmy and Mandy are his third cousins and his 7 times great grand children!! Crazy time travel problems!!