Percy Muir was born about July 1895 at Ellesmere Port, Cheshire. He was the son of John Muir of Glasgow and Jane Peddie of Holy Island, Northumberland. Percy's father was an engine fitter in 1901. By 1911 he was an agent, living in Linthorpe Road, Middlesbrough. He had had 8 children, 1 of whom had died by 1911, as had his wife Jane.

Percy joined the 1st/5th Battalion, Durham Light Infantry, Private 3080, April 17, 1915. Percy was killed September 18, 1916, age 21. His name is on the Thiepval Memorial, Pier and Face 14 A and 15 C.

Percy Muir is the great uncle of Heather Lawson of Brafferton.