Maybe Tanjiro is a Breath of the Sun user by using the Dance of the Fire God, Breath of Water and some saying/asking that he's using Breath of Thunder. I'm curious about it and correct me if I'm mistaken. Is it possible to use other style under of their Breath Style? Take a look in the picture below.
It was revealed in the latest chapter of manga
that Tanjiro is a descendant of the Breath Of The Sun User.
Can Tanjiro use the other Breathing Technique?
It is not yet revealed in the manga but Breath of the sun is the basis of all the breathing techniques and since the memories of the Breath of the sun users is passed down to the succeeding users we can all assume that he can use the other branches as soon as he completely inherit those memories.