Sam doesn't startle awake anymore. He's pretty sure that's a side effect of the whole 'sleeping with an archangel thing.' There are very few things in the universe that could sneak past Lucifer undetected, and if those things happen to get into Sam's bedroom, he's already screwed. He might as well enjoy his ability to actually get some good sleep in the meantime, even if that comes at the cost of Lucifer inevitably sprawling out on top of him in a way that should probably feel like he's crushing Sam. (Only, the weight of him inside his vessel, that unnatural angel density that Cas has tried and failed to explain, is nice. It's grounding. Sam's had few enough things in his life that make him feel safe, and it's taken him a long time to accept that Lucifer can be one of them.)
He wakes slowly, even with the sound at the edge of his hearing becoming impossible to ignore. He blinks up into the darkness once, twice, then fumbles for his phone. He manages to knock it to the floor. He curses. He's about to get out of bed before Lucifer makes a funny noise like a cat that doesn't want to be picked up, and Sam's phone is suddenly in his hand.
"Thanks," he says. Lucifer squirms closer and presses his face against Sam's shoulder. Lucifer seems to take offense at the idea of Sam's personal space. Sam doesn't think he'd be able to breathe in that position if he were human. Perks of being an angel. Sam looks at the clock on his phone. 3 AM. Witching hour. The noise that woke him rings out again, and he can tell that it's coming from the door to his room this time. No one other than family would come knocking this late. He runs down the mental list. Dean doesn't bother with knocking most of the time, and it's a little too quick to be Mom or Cas. Which leaves- "Your son is here."
"Before sunrise, he's Castiel's son," Lucifer mutters. Sam lets out a tired huff of laughter. Jack has recently discovered Disney movies, and Sam has since repeatedly caught Lucifer humming songs about animated lions. (And on one particularly rough night, singing to Sam to comfort him with what he only later realized was Can You Feel the Love Tonight.) The knocking comes a third time, this time accompanied by a small voice.
"Dad?" Despite his protest, Lucifer rolls off of Sam, but then he freezes. He just stares at the door that Jack is on the other side of. Sam's brain goes straight to old studies of dogs being shocked until they stopped struggling. Sam tells his brain to shut up.
He puts a hand on Lucifer's shoulder, squeezes once, and then gets up and walks past him to open the door. Jack's there, looking small and scared and every bit the child they sometimes forget he is when discussing the nuclear bomb of power he has inside him. Sam's not sure how Jack knew to come to his room when looking for Lucifer, (he'd thought they were keeping things well under wraps, enough to not freak Dean out, at least) but he chalks it up to some kind of latent angel instinct the kid has.
"I woke you up," Jack says, as though that possibility hadn't crossed his mind until he was looking at Sam, who was still rubbing the sleep out of his eyes. Jack ducks his head. "I'm sorry."
"It's alright," Sam says. "Come in." He opens the door wider. Jack peeks inside, still hesitant. When he sees that yes, Lucifer is actually there, he looks a little relieved. "So, what happened?" The lamp on Sam's beside table flickers to life without anyone touching it to replace the light from the hallway as Sam closes the door. The bulb whines in protest like it's considering bursting when it does so, and Sam frowns at Lucifer. The archangel does not meet his eyes, trying to watch Jack, and then failing to watch Jack, and finally letting his gaze settle off towards the opposite wall. Jack doesn't notice, at least. He's looking back at Sam again.
"Dean doesn't like being woken up in the middle of the night," he informs Sam, and Sam nods his most understanding nod, "so I couldn't go to Cas, because he's sleeping in Dean's room." Sam manages another understanding nod. He won't say he's surprised, because he's not, he is so far from surprised, but this is still information that he wasn't expecting to receive from his sort-of adopted son at three in the morning. "And I thought..." Jack trails off.
"Why did you want to get Cas?" Jack shifts his feet awkwardly. He's not meeting Sam's eyes, but that's not a product of nerves. He never looks directly at anyone, opting to stare at their shoulder or behind them instead. Dean says it's unnerving. Sam just files it next to other things, like Jack's hands flapping when he's excited or how he'd probably only eat one thing for a month if they let him, and saves the information for later discussion.
"I had a nightmare," Jack says, quietly, "and my room is very dark." Sam opens his arms up in invitation. Jack brightens, just a little, and accepts the hug. Sam catches Lucifer's eyes (he's looking back at them, expression a mixture of uncertainty and surprise) and tries to convey 'he's your son and he's upset, say something.' Lucifer makes a face back that roughly translates to 'I spent most of my life in the Cage or ending the world, I don't know how to deal with a child.' He relents at Sam's puppy-dog eyes.
"Jack. Come here." Sam can tell he's trying for warmth. It comes out stilted. Jack wiggles his way out of Sam's arms anyway and makes his way over to the bed. Lucifer pats the spot in front of him, and though Jack does sit there, neither of them look entirely comfortable. Jack rocks back and forth slightly. Sam comes over as well. It's not that he thinks Lucifer will do anything intentionally bad, it's just... There's a reason Jack's first instinct was to go looking for Cas and not him. Lucifer's been routinely terrible at this whole parenting thing. It's not for lack of trying, but he doesn't know what he's doing and next to Cas, who took to this whole situation like a duck to water?
Lucifer might be Jack's dad and nothing will change that, but Cas is Jack's dad too and nothing can change that either.
"You're one of the nephilim. You shouldn't be scared of the dark." Jack curls in on himself a little. Sam makes a cutting motion with his hand near his mouth. Lucifer tries to course-correct. "You don't have to be. You can make your own light." Jack tilts his head, shoulders still drawn.
"I can?"
"Of course you can, you're my-" Lucifer's voice stops before he can finish the sentence like he's been muted. He recovers quickly. "You're half angel. It's easy."
"Okay," Jack says, "but how?" Lucifer opens his mouth to answer and then shuts it again, frowning. "...Dad?"
"Give me a minute. It's been a very long time since I taught anyone how to do this." He shuts his eyes for a moment. Sam wonders how much of that hesitation is him actually trying to recollect and how much of it is him trying to push down the fact that the last time he did this was probably before he got thrown into the Cage. "Alright, let's see." Lucifer reaches forward and takes Jack's hands in his own. Jack jolts back in surprise, but then he leans forward again, curiosity overriding his shock. Lucifer has him cup his hands like he's trying to hold water in them. "This is all about intention and will, so focus." Jack's brow furrows in concentration.
Nothing happens.
Lucifer sighs, says under his breath, "Michael always was a better teacher than me."
"I don't get what I'm supposed to focus on." Jack breaks his position, shaking his hands out nervously. He puts them back in place when he's done. Sam would love to help, but it's been a long time since he had any sort of psychic power and that's not exactly a time in his life he wants to revisit.
"It's... How do I explain this to you." Lucifer rubs at his forehead. "No. I can't. It'll be easier this way." He gestures towards Sam's lamp, and the light dies. Jack inhales sharply, and Sam steps forward, reaching out in the dark to try and comfort the kid. Only, Sam blinks, and there is light. It's not coming from his bedside table or even the light above him. It's coming from Lucifer's outstretched palm. It's not a hovering ball of light like the cheap effects of some fantasy movie. Lucifer's skin glows from the inside out. It grows and dims in a rhythm not unlike a heartbeat, but never once does it waver. Jack stares, transfixed. Sam can't help but feel the same way. Lucifer glances up at him and preens under the attention. He reaches forward again to take Jack's hands.
"Does it make more sense now?" Jack nods.
"I think so." This time, as Jack concentrates, light does begin to flicker between his fingertips. "Is that right?"
"Yes. Keep going." Jack wiggles, all barely contained excitement, and Sam finds himself smiling. The light Jack produces is not as steady as Lucifer's, nor as bright, but still, Sam's room looks like it did before Lucifer turned the lamp back off. "Very good. I told you it was easy." Jack beams.
"It looks like Sam!" he says. Sam raises an eyebrow. Lucifer just nods.
"It does, doesn't it?" Sam's eyebrow creeps up higher.
"What looks like me, exactly?" Jack turns to face him, and Lucifer tilts his head. They're both grinning, and all of a sudden, the family resemblance is obvious.
"You're shiny!" Jack says.
"I'm what."
"We have always been mirrors, Sam. Are you really that surprised that your soul reflects how radiant I once was?" And Sam can't exactly say that he is, that he's spent his entire life thinking that he was sullied, not when Jack's right there. Lucifer smiles like he knows that, and he has so much trouble getting Sam to accept compliments normally that Sam's sure he's doing it on purpose. Sam counters. Turnabout is fair play.
"Mirrors only reflect what's still there, Lucifer." Lucifer pretends to take his words in stride, but Sam can see the few moments where he's caught off-guard by that. Jack looks between them, and then he ducks his head and bites his lip like he's trying to keep an even bigger grin from spreading over his face.
"Thank you," he says, "for teaching me how to do that." He rubs his hands together. "I can go back to my room now, I think." Sam looks at his bed (well, their bed, really. It's not like Lucifer ever really uses the one in his room.) It's pretty big.
"You know, when I was a kid and I had nightmares," Sam says, "Dean used to let me sleep in his bed." He's not sure if angels have childhood nightmares or beds to climb into, but from the way Lucifer's expression goes quiet and sad, Sam thinks he might have stirred up some kind of memory. "So, I guess, if you wanted to stay-"
"Can I?" It all but leaps out of Jack. He repeats himself a second later, softer, glancing over at Lucifer. "Can I?" Lucifer blinks, shakes whatever he was thinking of off, and nods.
"If it'll help."
Which is how Sam learns that Jack? Is even worse about personal space than Lucifer.
Still, even if he spends the rest of the night squished between the archangel he loves more than he's ready to admit and his son who's being collectively raised by the village of Winchester, it's worth it. Sam's happy. He's really, truly happy.