-They may apply for B2 visa, but they have to convenice the visa officer that they will return to China after their short visiting U.S.
如果為他們申請親屬移民有無可能?
-Yes.
大約要等多久?
-How did you get your GC? If your GC was employment based (i.e. I-140, then I-485), your family can get the immigration visa in China using following to join for about 6 months to one year by EB based category. Otherwise, you have to sponsor their GC application sung familfy based category which noramlly takes 5 years unless you become a US citizen.