Hally's father Guy Morrison Bryan (1821–1901) had emigrated to Texas in 1831. In March 1836, Bryan became the courier for at least one of William Barret Travis's Alamo letters from Bell's Landing to Velasco. He was an army orderly under Alexander Somervell, and in the Brazoria volunteer company under John Coffee Hays. He served in both the Texas House of Representatives and Texas State Senate. Bryan was a veteran of the American Civil War. He was a charter member and president of the Texas Veterans Association and charter member of the Texas State Historical Association.