Good piont!

well he probally could of but it prob wouldn't lisen bc maybe valdamourt did smth to the snake i havent read harry potter i only watched the movie so

It is because Harry does speak parseltongue, but it is under control of Tom Riddle. He is the heir of Slytherin (well, the Guants are related to the Perevalls, like Harry, but he isn't a direct heir of Slytherin, so it doesn't count.)