Tonyn was from a military background. His father, Charles Tonyn, was a Colonel in the 6th Inniskillen Dragoons. Patrick Tonyn became a captain in the 6th Dragoons in 1751, with which regiment he served in Germany in 1758 during the Seven Years War where, in 1759, the regiment fought at Minden and Wetter with great distinction. Tonyn was made lieutenant-colonel of the 104th regiment in 1761. Patrick Tonyn was born in Berwick-upon-Tweed in Northumbria and died in London on the 30th December 1804.