He or she is your great-niece/nephew
Your sister is great aunt to your daughter's child. The child is your sisters great nephew (if a boy) or great niece (if a girl).
Your daughter and your sister's child are first cousins. Your daughter and your sister's grandchild are first cousins, once removed.
None of the Cimorelli sisters have a child.
No Justin Moore is an only child and Kip has 2 older brothers and 3 younger sisters.
cousin
brother-in-law
Great neice
sisters
Your sisters daygter is your neice!
Sisters
Second cousins.
She has her sisters child, because she and Eminem adopted her (Alaina) ;-)