The Shah of Iran had several attempts on his life. The last one was by a nephew.
There was the royal family in Nepal, etc. etc., too.
If the West does decide that it is in fact time for the Chia Pet to leave the scene, and I mean like, for GOOD...and they have constructed an acceptable succession scenario in view of the nukes, then expect one of Kim's family members to do this in the next year or so.
Probably quite a huge performance bonus and career promotion waiting for the staff and management of the agency or group in the West that successfully pulls that off.