Sweden and Finland?
Though neither country is a NATO member, they have both had a long history of cooperating with NATO.
Sweden has not been in a war for two centuries. Its last war was in 1814, against Norway, in the Napoleonic Wars. Sweden stayed out of both WWI and WWII, and over the Cold War, did not join NATO.
Finland was ruled by Sweden in the 18th cy., then by Russia in the 19th cy. as the Grand Duchy of Finland. Toward the end of WWI, Finland became independent. In WWII, Finland fought the Soviet Union, losing some territory in the southeast, including the city of Vyborg / Viipuri.
During the Cold War, Finland had a policy of being conciliatory to the Soviet Union no matter what, and many people feared that other European nations may end up doing that, something they called "Finlandization".