It was the first preseason game for both teams.
Jackson Cates scored the game-winner at 15:20 of the third period, deflecting in a point shot by Egor Zamula from the slot.
Noah Cates gave Philadelphia a 1-0 lead at 1:42 of the second period on a 5-on-3 power play. He scored at the back door off a behind-the-back pass from Morgan Frost across the top of the crease.
It was the first time the brothers played in the same NHL game.
Felix Sandstrom made 17 saves for the Flyers before being replaced at 6:29 of the second period by Troy Grosenick, who made 14 saves on 15 shots.
It was the Flyers' first game under coach John Tortorella, who watched the game from the press box. Ian Laperriere, the coach for Lehigh Valley of the American Hockey League, served as coach.
Jakub Lauko scored, and Keith Kinkaid made 14 saves on 15 shots in 29:57 in his debut for the Bruins after signing a one-year, two-way contract July 13. He was replaced by Kyle Keyser, who made 13 saves on 14 shots in Boston's first game under coach Jim Montgomery.
Lauko tied it 1-1 for Boston at 12:50 of the third, scoring from the high slot after he knocked down Josiah Didier's shot attempt from the point.
The Bruins were 0-for-6 on the power play, and the Flyers were 1-for-5.
