Click here to reveal spoilers for Dragon Age: Origins.
Kinnon is one of the few survivors inside the Circle Tower during the events of the Broken Circle. If the Warden decides to help Wynne, they can speak with Kinnon about the events in the tower. He will also mention that Wynne had told them about Loghain's treachery.
If the initial conversation with Wynne goes sour and she attacks the Warden, Kinnon will assist her, along side Petra and Keili.
Additionally, when fighting Shah Wyrd in order to obtain Yusaris, he will assist you.