Board Thread:Speculation House/@comment-24.247.91.107-20140511154823/@comment-4010415-20150605074340

"He wouldn't tell me everything, but I learned that the two of them had been on a team together with Summer and Qrow, and that she'd left me with him right after I was born." - Yang Xiao Long, in Burning the Candle. Direct link

So, yeah, Yang's mother was on the same team as Summer, Qrow, and Taiyang.