Nisiewicz is a correct form
Nisiewicz is a correct form. Other spellings of this name:
Niesiewicz, Niesiejowicz, Nasevich (as spelled by some in Olyphant, Pennsylvania), Nisievitch, Nasevitch.
All forms come from: Nisiewicz (spelling in Polish).
The name originated in Dobra Szlachecka: www.dobra.org