Matsunosuke is simply the name of a sanke bloodline created by the Sakai brothers. The Matsunosuke sanke was so successful that it shot them to fame. The name of the farm is Yamamatsu. I only learn of this about 2 years ago... before that I thought the name of the farm is Matsunosuke
It's just like the Sakura bloodline from Sakai Hiroshima that spawn the now famous Rose line of kohaku.
-Dennis