The late rapper's sister Samantha Smith recently submitted legal documents to LA County Superior Court, according to TMZ.
Insiders say that Smith is concerned that Emani's biological mother Tanisha is not fit to care for the child.
It's reported that Emani was being cared for by her father prior to his March 31 death.
Smith contends that she should takeover the role of caretaker since she has helped care for her niece for nearly all the child's life.
The rapper's sister is hoping 'to ensure the continued stability for Emani and ensure that she will be able to maintain [their] current and ongoing relationship.'
A judge has yet to rule on the matter.
Nipsey also has a two-year-old son, Kross, with longtime girlfriend Lauren London.