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“You need to stop this, Nephew,” Peter keeps his voice calm. He has no desire to wake the sleeping boy in his lap with this discussion even if the boy has permitted—and encouraged—him to have it.
Derek is sitting across from him. The loft had been furnished years ago, and the remains of a pack meeting are scattered around the living room in throw pillows on the floor and empty pizza boxes on the coffee table. Stiles had fallen asleep a little over an hour ago, and when the movie ended the rest of the pack had quietly slipped out of the loft so Stiles could doze on.
Derek has not stopped staring at them since Stiles crawled into Peter’s lap and demanded he be cuddled to sleep. They have been together long enough that the pack no longer bats at an eye at them showing affection. It hadn't been smooth at first, but so many months later and no one is bothered. No one but his nephew, who has protested their relationship since he first smelt Peter on Stiles' skin and pinned him against a wall with claws at his throat.
Derek, who smells of peppery interest every time Stiles brushes by him, or shows up in the well-fitted wardrobe Peter keeps for him in his apartment. Derek, whose interest in Peter's mate has become more and more obvious since they got together. Derek, who is glaring at them now while reeking of jealousy.
“You have no reason to be upset by mine and Stiles' relationship. The rest of the pack has gotten over their grievances, I am sure it is time for you to do so as well.”
“It doesn't upset me,” Derek growls lowly. Peter acknowledges his denial with a roll of his eyes as he ponders on what he wants to say, on how honest he is willing to be.
“You need to move on,” Peter scolds. It's a tone he has not taken with Derek since he was a boy. It is strange to use it now, so many years later and so many lives lost. Peter takes a deep breath and pulls in Stiles' scent, allows himself a moment of weakness in which his mate’s scent and the heavy warmth of him draped over Peter's lap gives him the strength to say what he's been feeling for far too many years. “You need to move on or you need to join us.”
He may be watching Stiles' face and the sweet flutter of his lashes as his eyes move in his sleep, but his other senses are fine-tuned on Derek. The Alpha tenses, his heart rate rocketing as his scent...it doesn't sour, not quite, but it does change to something Peter cannot quite make sense of. “What are you...”
“There is no future with you and Stiles in a monogamous relationship. Stiles is my mate and I am his. But we love you, Nephew.” The term doesn't cut, not like it had for so many years. Not like it had when Peter wielded it as a reminder to himself that he could never get what he truly wanted for who Derek was to him. Now, he shapes the word without the sharpness he has for so many years, and it nearly sounds like an endearment. “You may join us, should you chose to.”
“I—” Derek falters. His voice breaks and his scent floods with embarrassed uncertainty.
“I am not lying to you,” Peter tells him before Derek can begin to overthink things. He keeps his voice as even as his heartbeat, both ringing true. “We love you. I...love you. I know you are familiar with triads and that is what we are inviting you into. We are inviting you into a relationship with the both of us.”
Peter hears him swallow, though he keeps his eyes on Stiles' face. The boy has done more for him than Peter could have ever imagined. Has healed him in a way that Peter never could have hoped for. The bond they share is bright enough that Peter can ignore the dimness in his chest where his family once lived. Stiles snuffles, his lips parting sweetly before he lets out a quiet snore that makes Peter's chest ache sweetly.
“He loves you,” Peter says quietly. “I love you. I don't know exactly how you feel about us, but you flirt with him and you scent him as though you are interested. He sees it and the pack sees it. I see it.”
“I'm sorry—”
“You aren't, but that is okay. I certainly understand the appeal,” Peter allows with a tilt of his head. His brushes his nose over Stiles' temple just to feel the heat of his skin and tries to settle himself. “Just know that being with us, together, is an option for you.”
“Can I...think about it?” Derek asks. His voice is laced with a fear that Peter understands. One that has his fingers shaking where they're wrapped around Stiles so Derek cannot see.
“You may think about it for as long as you need, Derek.” Peter finally allows himself to look up. Derek is watching him with rosy cheeks hidden behind the beard he's grown out. His eyes are full of a wonder Peter has not seen since his nephew was a boy. It has his heart turning over inside his chest, loathe as he is to admit it.
“I love you,” Derek says quietly. His voice breaks, and he sounds like the boy Peter remembers him being. “I love you so much. I think I love Stiles. But—”
“Love has caused you pain,” Peter finishes for him. Even if they are not as close as they once were, Peter can still read him. It helps that he feels much the same. “We both know that. We understand that. We love you, and we want you to be happy above all else. If that is with us, we would be overjoyed, but if it is not...it would hurt, yes, but we love you. Your happiness is what matters most.”
“Thank you,” Derek whispers, and the word is heavy. They watch each other for endless minutes that leave Peter feeling like he's reeling from the impact of Derek's words. It is something he has wanted to hear for so long, and now that he has, the words, as simple as they are, feel like a gift he that he does not deserve. It is Derek who looks away first, though Peter does not let it bother him. Not after the last few minutes. “I think I'm going to head to bed.”
“Alright,” Peter tells him, “I hope you sleep well.”
Derek nods his head, but he doesn't say anything else. He stands silently and walks over to them without a sound. Peter tenses and then forces himself to relax as to avoid waking Stiles. When Derek's fingers skim along the back of his neck, he has to bite into his lip to hold down a whimper that his wolf desperately wants to let out. Instead, he tilts his head to the side to give Derek room that he takes, firmly gripping Peter's nape as his thumb strokes the skin behind his ear gently. Peter shivers and does his best to hold still.
“Goodnight, Uncle Peter,” Derek says on an exhale. Peter rumbles in response, unable to form words with the weight in his chest that being called Uncle Peter bring him. He listens as Derek walks away and waits until he is in his bedroom to tighten his hold on Stiles and bury his face into his boy's hair, breathing him deeply and allowing a shuddering breath to leave him.
Stiles shuffles and curls impossibly closer into Peter's lap, and it feels as though his chest breaks open, his heart filling with more love than he knows how to hold. He breathes deeply, Derek's scent mixing with theirs from where he had left it on Peter's skin, and he allows his eyes to close while his lips tilt up.