A Michigan teen who has made annual treks carrying his younger brother on his back to raise awareness about cerebral palsy on Wednesday started a 111-mile walk that's expected to be his last.

Hunter Gandee, 16, set out from Temperance in southeastern Michigan while carrying his 70-pound brother, 9-year-old Braden, who has cerebral palsy and can't walk without assistance. The brothers expect to reach the state Capitol in Lansing on Monday, stopping at schools along the way.

Hunter expects this will be his last such walk because he will be starting his senior year of high school in the fall and will be preparing for college.

"And Braden is getting bigger," Hunter added in a telephone interview with The Associated Press on Wednesday.

Braden plans to complete the final half-mile in Lansing using a walker.

"He's pretty excited right now," Hunter said. "We've had a great time, so far."

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They call the walk the "Cerebral Palsy Swagger," and it challenges people worldwide to take steps toward inclusion.

"I'm extremely thankful for our support and that has inspired me to keep going," Hunter said.

Hunter was 14 in 2014 when he carried then-7-year-old Braden for 40 miles. Last year, they made a 57-mile journey.

Two years ago, Hunter held Braden in his arms on the mound at Comerica Park as Braden tossed the ceremonial first pitch in Detroit's Tigers game against the Colorado Rockies. He and others also raised money last year for an accessible playground at Braden's school.