S2 visa to visit my girlfriend?

Hey, I need a little help answering a question I'm unsure about. I'm planning in visiting my girlfriend, a Chinese national who lives in Shanghai, for up to 90 days this summer. Is there any way I can apply for an S2? I know it's commonly for spouses and family members but it also uses the ambigious term, 'other private matters'. My girlfriend and her family would be completely happy to supply any necessary documents if it helps.
Cheers