I think that the Haven is not a single location but a network of interconnected hiding places. Each is connected by Portal to at least one other, but only a few have direct access to the outside world. Joram is probably the only person who has knowledge of all the locations.
If I recall correctly, the location mentioned at the beginning of KJY is at Trevalga in the Connait. Gregory Earl of Ebor moved his family there for safety and seclusion. I think that the St. Kyriell's found in QFSC was once part of the resistance and escape network.