I have met several of them and they are not socialists, but on paper you are right. Both are historically related to http://en.wikipedia.org/wiki/Socialist_International and PUK is a member.
The reason was to get funding from Europe, especially from France. PKK was funded by KGB. http://www.freerepublic.com/focus/f-news/1911724/posts
Politicians follow money without a care as to what the people think. What about the leadership?