4 the moment no one. at least that's what known por the midea. snsd's members dont own their time...they are always very busy. + sm forbid them from dating ...so they can give 100/100 in their preformance.
So far it seems like Taeyeon, Tiffany, and Hyoyeon have without a doubt had boyfriends. I don't know about Seohyun, Sooyoung, Sunny, or Jessica who haven't talked about a potential amor or pasted lover.
Yoona has lee sung, Jessica has Tyler Kwon, a non-celeb. Now nearly every Korean dislikes him because of Jessica's departure form GG Tiffany had Nichkun from 2pm (another kpop group) now they broke up:( I miss fanykhun moments Taeyeon has Baekhyun from exo, another popular kpop group. However unlike Tiffany and nichkun, they receive so much hate. Sooyoung has a boyfriend but not sure who it is Hyoyeon has an ex-boyfriend Yuri has a boyfriend who is a professional baseball player Hope this helped:)