I have no idea if there is a relation or not. My grandfather, Joseph Niamtu was born in 1890 and came to the United States about 1915.He went back to Romania, married my grandmother and she came over about 1920.
He was one of 7 sons and was the only son from that family to ever come to the United States. With him being in the U.S., if any cousins, nephews, etc. ever came over, I would imagine they would have contacted us. Everyone who came was assisted by family that was already here. Next to Detroit, Ohio has the largest Romanian/American population.
Perhaps Niamtu is a relatively common name in Romania.