Kath was already doing the job for Hull in her capacity as chairman of the club, and she will now be joined by Gary, who is chief executive at Headingley.
The Leeds chairman, Paul Caddick, has led out the Rhinos for their last three finals, but he has stood down to allow the Hetheringtons a unique double role.
"It's strange we find ourselves in opposite camps for such a major event," said Gary. "We are used to it happening at league games but it has never happened on such a significant day as this.
"It's been terrific that we share the same passion and involvement in rugby league. It's a great honour to lead the team out at the final. The Challenge Cup is a unique and special occasion."
The two will travel to the Welsh capital separately with their clubs tomorrow and will only meet briefly at an official lunch on Friday before leading their teams out at the Millennium Stadium the next day.
The couple's division of loyalties also creates a split within the family, with their daughters, Lucy and Polly, supporting Leeds, but their brother, Matthew, and Kath's Auntie Dot loyal to Hull.
Kath, who has been chairman there since the merger with Gateshead in 1999, is splitting her responsibilities with one of Hull's most enthusiastic fans. Scott Walker has cerebral palsy but he will lead out Hull in his wheelchair.
A scan on Keith Senior's ankle has revealed no break and his participation for Leeds in the final now depends on how quickly the soft tissue damage around the joint improves.
Senior would be the one player in the final who also appeared for Sheffield Eagles when they won the Cup in 1998 under the coaching of John Kear, now in charge of Hull.
Another Leeds player, Willie Poching, was having an X-ray on his fractured cheekbone last night that will determine whether he will be in the 20-man squad that both clubs will name today.
Hull, without any major injury worries, must decide who to leave out, but Kear has dropped a strong hint that Danny Brough, who was playing in National League Two with York City Knights a year ago, will be in his side and could even be his first-choice goal-kicker.
"He's blossoming all the time," he said. "He's played 20-odd games for us. I didn't expect him to play that many, but he's playing so well that he demands to be picked."Reuse content