Advisors makes sense (I guess envoys use them too), but why leaders? Because there is a separate block with leader names
Agents, generals and republican rulers are monarch name (first name) + leader name (last name).
You can end up with one of these on your throne though as i believe pretenders get their name this way (didnt check though), while "an important noble" successor as well as newly created states will use the culture dynasty list.
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