Both local development of a nuke and the receipt of a nuke by other means will resolve Yes. A nuke that legally belongs to another country but is consensually stored and ready to use in the territory or on weapons platforms belonging to a new country will resolve Yes, as will any other new or revealed nuke-sharing.

So if the Cuban Missile Crisis happened tomorrow, Cuba would resolve Yes. The same for the First Taiwan Straight Crisis. Likewise, Canada being revealed to secretly keep US-owned nukes in their territory would resolve Yes even though they were previously denied. Past shared weapons do not count.

When there is ambiguity as to whether a country actually has nukes or not, non-proliferation groups will be given priority as to their opinion. If you add a country, please check that they are not already widely understood to currently have or host nukes.