Lucian listened for the noise that had awakened him. Nothing but silence penetrated his sister’s house. The blazing hearth fire saturated the room with heat, but Catarina forbade the opening of windows. His twin was always cold.
I'm really dense today-- I thought there were four people: Lucian, his sister, Catarina, and his twin. I mean it-- my brain feels like oatmeal. If I were a bit sharper, I'd probably have understood. :)
However, twin and sister-- don't use both. One, we can assume equals Catarina. So how about simplifying:
Lucian listened for the noise that had awakened him. Nothing but silence penetrated his twin sister’s house. The blazing hearth fire saturated the room with heat, but Catarina forbade the opening of windows because she was always cold.
This doesn't seem unified. He wakes up because he heard a noise. Then he feels the heat and thinks about his sister. Finish up with the noise. I can't say this enough: Be in him. Be him. He hears a noise. It wakes him up. What does he do? He sits up in bed? He cocks his head to where the noise came from? He listens hard? When he hears nothing, what does he do? Does he try to figure out what the sound was? (After all, not all sounds are recurring.) Does he swing his legs off the bed and lean forward or stand up? If you want to have that about the room being warm in this paragraph, how about showing it in action-- he throws off the covers because he's so hot?
Don't summarize important action. Let the reader be in his body, let him act the way people act when this thing happens. Don't take it too far, but what does a person do when he's awakened by a noise? He probably does more than just lie there. (We react instinctively to a noise at night, like the smell of something burning, because these are signs of danger. They will wake us out of a dead sleep. But because they are signs of danger, we aren't just going to lie there-- we'll do something if only to get more information. We won't settle back into bed until we have convinced our jangling instincts that we are not in fact in danger. This is primal, and you probably really need to have him act a bit on it, figure out that the doors are locked still and that the noise was just a branch against the window, not Jason in his hockey mask. :)
(Understand that the TSTL heroine is based on me. -- Too Stupid to Live.-- If I heard a nighttime noise in the attic, there I'd be, climbing those attic stairs, because my fear of the unknown is greater than my fear of Jason and the hockey mask.)
Also, if the room is too hot, he's going to do something, not just lie there and think about his sister. He's going to throw off the covers, pull off his shirt. Decide he'll risk Sis's wrath and open a window.
Now you might say, geez, that's a lot for one paragraph. Yep. That's why you should put the noise, the awakening, the listening, the sitting up, all the noise stimulus and reaction in one paragraph, and have another about the heat, and his reaction to that. Get him moving. You don't want him confronted with two physical stimuli and commit no action at all. His body does more than just perceive-- it moves too.
The blazing hearth fire saturated the room with heat, but Catarina forbade the opening of windows. His twin was always cold.
The diction is a little formal here (which is fine), and longer sentences are common in formal narratives. But still trim out the words that aren't needed. "forbade the opening of windows" is sort of clunky. And the connection between the two clauses isn't all that clear. Apparently he WANTS to open the window, but remembers that his sister doesn't allow that (and you've said it's her house-- so her rules). Do you see what I'm going to suggest? Show him thinking about getting up and closing the window. Then the thought about her forbidding opening the windows makes more sense. Like:
The blazing hearth fire saturated the room with heat, so he got up and started for the window. But halfway across the stone floor, he stopped. Catarina wouldn't stand for that. She forbade the opening of windows because she was always cold.
Catarina sounds like a really lousy hostess. She's cold, so all her guests have to be miserable?
Actually, I have a relative just like that. She keeps her thermostat at 87. Really. I always make excuses to get out of there and spend the night elsewhere!