The Territories beat B.C.'s Jim Cotter 8-3 to capture the fourth and final playoff berth.
It's the first time since playoff games were introduced to the Brier format in 1980 that a Territories team has made the playoffs. Don Twa's Territories team finished tied for runner-up in 1975 when the event was a round-robin format.
Koe, whose Yellowknife team finished 7-4, joins brother and Alberta skip Kevin in the final four and will face him in a Page playoff between the third and fourth seeds Saturday.
Ontario's Glenn Howard (10-1) and Manitoba's Rob Fowler (8-3) meet in Friday's playoff between the top two seeds. The winner goes directly to Sunday's final. The loser drops to the semifinal and faces the winner of Koe versus Koe.
Alberta lost 6-3 to Ontario in the final draw of the preliminary round Thursday, which dropped Kevin Koe's team to third at 8-3.
Note to readers: This is an corrected story. A previous version had Ontario's record at 9-2.