The club made the announcement following the decision at its’ annual general meeting this week which will restore the former Scotland international’s connection to the Greenyards, where he played for six years in the early nineties.
Weir, who has spent the past four years raising money for motor neurone disease charities following his diagnosis with the condition, said he looked forward to sharing the responsibilities with the Duke.
In a video message he said: “I’m delighted to become joint honourary president, thanks so much to all involved.
“I’ve had some amazing times while playing at Melrose and I’m so excited to relive those playing days with my boys now.
“I enjoy coming down to the club, its a very special place to be.”
The club has also confirmed the return of the Melrose Sevens, in April next year.