It would depend on the person. If a citizen of another country applied for an NIN, they will be issued an NIN based on their citizenship. However, let’s assume that they become a Kaldan Citizen. They will then receive a Kaldan number. Unless they renounce their citizenship with their previous country, they will now have 2 NINs. The foreign NIN remains as it is likely to be a telephone number, and a bank account. They could essentially get 2 telephone accounts with 2 unified voicemails, but this will likely be rare. In most cases, the citizen of another country will just keep their current numbers, and identification. However, they would need to work out the situation that is based for them.
Since they are still one person, they will not receive a new GIN. Instead, they will navigate the 2 NINs as needed. The GIN is tied to the person where the NIN is tied to the nationality. It is pretty simple.