LaDube, whose real name was Nothando Dube, succumbed to an illness related to skin cancer while undergoing treatment in a South African hospital on Wednesday.
She was 31 years old.
The death was confirmed by Traditional Governor Lusendvo Fakudze who placed an announcement of her demise on the eSwatini Broadcasting and Information Services (EBIS) on Thursday.
“The funeral of the Inkhosikati will be on Sunday after a vigil that will be held at the Ludzidzini Royal Residence," the governor announced.
Between 2011 and 2012 the late Inkhosikati once stayed away from the royal family for about a whole year and during this time she was living in South Africa, following an incident that led to a cabinet minister who was also a childhood friend of the king being fired.
Inkhosikati LaDube was 16 years old when she joined the royal family and eventually got married to the king in 2005.
She was fresh from contesting in the Miss Teen Beauty Pageant where she made it into the finals.
Her death comes exactly 11 months after that of Inkhosikati LaMasango (real name Senteni Masango) who died in the first week of April in 2018 after a suspected overdose of about 40 amytriptyline capsules she was taking for a mental health condition.
The king is now left with 13 wives and a fiancee, LaMashwama