Many err and call him Bill Gates II.
His father Gates II is active in politics and is dumber than a democrat running to abolish ICE.
Because so many address him erroneously as Bill Gates II, I aim to correct people just like you by referring to him as Gates III.
I've never referred to Bill Gates as "Bill Gates II", nor have I ever noticed anyone else refer to him that way.
I'm pretty sure that 99% of the planet just calls him Bill Gates.