Solas knew.
At first, of course, it had just been speculation, but soon he learned to understand the subtle hints that gave way to deeper secrets. Secrets that, if revealed, could cause certain problems within their carefully crafted group of ragtag heroes and allies.
It had been around midnight the first time his suspicions had been confirmed. Upon looking up to the library balcony at the sound of giggling, Solas had been quick to exit his small study at the sight of their elven Inquisitor's small body pressed back into the wooden balcony, his pale lips claimed by none other than the muscled and mustachioed Pavus he had come to recognize as complete and utter trouble. Perhaps Inquisitor Lavellan didn't realize such yet. Or perhaps he was looking for exactly that; trouble and danger in the form of charm and beauty. If that was so, he'd found the perfect man to fulfill that desire.
However, if Solas had been honest with himself, which wasn't a lot, he would say that he'd known all along how that man –Dorian, the Inquisitor was always trying to correct him– had been having his way with the fade-marked boy for a long time.
There were just certain...ways, that he knew. Like, for instance, how the Inquisitor would slow his run to a walk all the times he and Dorian came down the library stairs, smiling drunkenly, as they pulled and tugged each other to the door by their tightly-joined hands.
Or maybe it was simply how many times he overheard their leader asking to 'steal a moment alone' with the man. 'Talk', he had requested previously. Solas nearly laughed at the thought.
...Nearly.
Of course, by now he knew, though, that anything remotely close to 'talking' was definitely not what those two were doing in their time spent behind doors, closed or not.
He knew it in the way he had to carefully dance around explaining to Josephine that the pleasure-filled screams in the night were not, in fact, from their leader being assassinated. Assaulted, maybe, but not murdered like those hoarse yells would've been more proper as. Though, even that might not've been the right word. 'Willingly ravished' might've been correct, if Lavellan's wealthier dressing maid was any indication. Solas nearly lost his appetite thinking about what that poor elven girl must've been paid to clean in that room.
Whether or not they knew his new-found knowledge was lost on him, but if they did know, he hoped the two didn't expect him to keep this secret forever. Not that he would ever tell. Solas just hoped that their nightly –and daily, when Dorian obviously felt like he'd die if he couldn't get inside their Inquisitor– sessions, as he'd call them, didn't interfere with defending the world from the danger of the Fade rifts and Corypheus.
Nevertheless, Solas kept the secret of the two. After every small journey he took with the young Dalish, Dorian included or not, he made sure to suddenly need assistance from whoever wanted to interrupt the elf and his human lover from having their time together. He would do that; help their relationship along in whatever little ways he could. But that didn't mean he supported it. He was just making sure the small phase (for that could be all it was) went along smoothly. No need for unnecessary heartbreak.
But the next time Solas heard that panting and gasping, and the hushed and breathless chuckles of "Quiet, Amatus!" coming from the empty library after dark… Well. Let's just say that he would lock the door on his hastily-made way out.