The couple's Pico dinghy had filled with water 45 minutes earlier. While they were wearing life jackets and didn't believe they were in life-threatening danger, they were in danger of losing their water-filled boat.
Stuart was enjoying the sunshine in his 8-foot dinghy when he spotted the distressed couple.
"He's only allowed to go down as far as Fishcombe Cove. This is the first year he has been allowed to go that far, but he spotted the sailing dinghy in trouble about half a mile off Fishcombe," Stuart's father, Nigel, told This is South Devon.
"He rowed out to see what was going on as it kept turning over."
Stuart told BBC News that he went to their aid "because I was there, and I care about people, and they were in danger. I just put them on tow and brought them in."
Stuart towed the couple's boat back to shore, a 30-minute half-mile trip that was, at times, against the tide.
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Brown called Stuart "an absolute star" and thanked the young hero with boxes of sweets.
While Stuart was concerned his parents would be upset that he went too far out to sea to reach the couple, Nigel insists they are "very, very proud of him."
"I'm used to it because my brother is part of the Torbay coastguard team and my dad is on the Torbay lifeboat, so I'm used to it, really," Stuart told the Press Association.
Stuart's mother, Cheryl, added, "Like father, like son."