I guess this is more of a backstory/personal canon.

On my second playthrough I went with a standard 2h warrior human and instead of rejecting the Chantry and the Maker, decided to embrace it.

I was thinking how often the Templars are shown in a 1 dimensional light. Like yeah, you have the very few exceptions like Cullen or Allistair, but they became ex-Templars and got away from the Chantry. And typically you're seeing the perspective of the put down mages such as in Kirkwall or during the demon uprising in DA: O. But how do you think most people unbiased view the Templars? How do most Andrastians view the Templars? not as evil, but as real protectors.

Originating in the dual walled Free Marcher city of Ostwick, the Trevelyans are a noble house noted for their piety and connections within the Chantry and the Templar Order. Younger members of the family are often expected to follow a career in service of the Chantry either as a member of the Chantry itself or as a Templar, regardless of their personal feelings or motivations

So maybe Inquisitor Trevelyan was born in a very faithful Andrastian noble house. Maybe he had been brought up being taught that the Templars were heroes and were there to protect the people from the constant threat of demons and blood mages, which isn't false but maybe not as hyped up as everyone is at the moment.

I imagine that Inquisitor Trevelyan's father was a Templar, a Knight Commander that watched over his own Circle in the Free Marches. It's not said that everywhere the Templars and Mages had bad relationships so maybe he was one of the good ones, actually respecting and being professional with the Arch Mage of that particular Circle. When the revolution started in Kirkwall and all the Mages were called to arms, Trevelyan had a difficult choice and sadly became a victim of the uprising.

Inquisitor Trevelyan's two older brothers, both brash and headstrong, decided to enter the conflict as they were templars too. They were never heard from again, it's unknown whether they're still alive or were swept away.

When the Conclave was called, soon-to-be Inquisitor Trevelyan, as the last male heir of his house, knew he had to be in attendance for the memory of his fallen family. He wasn't jaded against the mages because he was raised in the Chantry and alongside his father in the Circle and brought up knowing that they were people but that to let them have free reign could lead to disaster. (See Tevinter Imperium)

So yeah, that's my story for my Inquisitor. He doesn't blame the mages or the templars, but knows the conflict must be ended so that peace and normalcy can be returned. I guess he wants to set the example his father set before him.

/end