Not sure yet, but is this the title of the soundtrack for them: Yosuga no Sora Blu-ray Kazha Migiwa Soundtrack and Yosuga No Sora Blu-ray Nao Yorihime Soundtrack
Note: Im note sure of the quality of certain tracks since I took this ost from an unknown site so just tell me if its good enough. If not, I can get a better version next time.