It has the eight planets and a host of asteroids and cometary bodies. But no, our sun is essentially a solitary star. Stars with companions are known as binary stars, or trinaries, etc.
Nothing is known about any companion star. There is a "Nemesis hypothesis", according to which there could be one, but no companion has been confirmed.
of course not. But the sun is somewhat special in the fact that it is a lone star, most stars exist as part of binary or tertiary systems and other multi star clusters.