You do, by switching back to his mouth instead

No matter what you just did to him, Nick is still your precious baby brother, and those protective feelings remain as strong as ever. As tempting as it is to break him entirely in one furious night of passionate butt-fucking, you decide to hold back for now. The pleasure you’ve already given him should keep him firmly away from those unsuitable tattooed skanks. How can licking some nasty girl’s pussy compare to having his butt broken in by his older sister’s massive cock after all? Still, the throbbing erection hovering in front of you does demand some relief, and you want Nick to understand it’s his job from now on to keep your balls drained and your cock soft and satisfied.

You keep stroking his back, feeling him shiver cutely and listening to his soft moans. He sounds so adorable, it’s almost a shame to stuff his mouth full, but the aching need in your balls doesn’t give you much of a choice. You just dumped the largest, most satisfying load ever in your baby brothers butt, yet your arousal hasn’t faded in the slightest. It’s like your body has secretly longed for this so long that it’s not about to let you even think of ending any of it until you’re well and truly satisfied.

“Little brother.” You coo softly, your hand running up to grab him firmly by a handful of soft black hair. “I’m not finished with you just yet.”

“Lucy...” He whimpers, his bleary eyes fluttering up to your face. He looks so cute and silly you can’t help but giggle, the way his mouth lolls open and his soft tongue dangles free, the pink flush colouring his smooth cheeks and the sheen of sweat on his forehead. He’s been fucked out of his little boy brain and he’s never looked more adorable for it.

“Here you go.” You smirk, moving his face gently towards the swollen, glistening head of your cock. “Suck.” It’s just been buried to the hilt in his butt, yet Nick doesn’t even hesitate, his mouth stretching wide open so you can slide your cock between those lovely soft lips. You feel like a nice, lazy blowjob this time, so rather than just shoving your shaft down his throat you let him tenderly suck and lick at the tip, worshipping your cock the way a good boy should. You make sure to keep rewarding him for his good behaviour, using your other hand to rub his neck and back and cooing soft encouragement, telling your little brother how good his mouth feels and how right and proper it is that it be used as a warm, wet home for his older sister’s cock whenever you want.

After a few minutes of that, you feel like something rather different and slide your cock free. He lets out an adorable moan of disappointment as it pops from between his lips, the swollen head glistening with his saliva.

“Don’t worry.” You chuckle. “I’ve got something else for you to do with that sweet mouth, little brother.” You raise yourself up on your knees, pulling him by the hair down under your throbbing erection and pressing his pretty face right against your hot, swollen balls. “Lick them.” You purr, a hint of sharp command in those words. He doesn’t hesitate, nuzzling into your sweaty sack and tenderly licking at the skin with his deliciously soft tongue. He focuses on each heavy ball in turn, kissing, licking and sucking them in ways that make your toes curl. The feeling makes you growl with pleasure, so much better because your it’s your cute, darling baby brother worshipping your balls. You’ll have to make him do this often, you decide. Maybe next tome you’re working on some particularly difficult paper, you can have Nick kneeling between your legs keeping your arousal simmering away before you fuck him later.

Your hand darts down to your aching erection, and you start to slowly pump your fist along the length, jerking off above Nick’s head as he keeps making out with your balls. His tender nuzzling feels so good you decide you don’t even want to finish in his mouth this time. Instead, he can feel your balls tighten in his lips as you spray down his slender, bare back. Spurred on, you rub yourself faster. Even your achingly sensitive pussy is clenching tighter and throbbing as Nick’s soft tongue drifts down under your heavy balls, resting them on his pretty face. You don’t want him licking you there, it feels too much to even touch with your fingers, so you pull him back by the hair and keep his focus on your balls where it belongs. He takes one heavy orb in his mouth, his hungry moans vibrating through your skin.

That delicious feeling sends you over the edge, your balls aching and tightening. With a hot groan, cum sprays violently from your pulsing cock in a series of shuddering jets. The pearly liquid spatters across the skin of your baby brother’s back, a good amount making it down as far as his butt and thighs. You sigh with warm satisfaction at the sight of his plump cheeks covered in drops of your cum, the delicious post-orgasmic relief all the better since Nick is still lovingly sucking on your balls. Such a good boy. You affectionately tousle his hair.

Your cock is finally starting to soften, wilting down over his head to settle in his soft hair, drooping over him. Your arousal ebbs away to cooling embers, and with it fading you feel the urge to sleep sweeping over you before any other urgent questions can intrude beyond flickering on the edge of your mind like blaring sirens far off in the distance.

Like just what the fuck you’re supposed to do now? Or even what the Hell you were doing getting so aroused you just fucked your own brother. It should disgust you, you know, but with Nick still happily sucking on your balls you find you just can’t feel that way yet. Vague thoughts about the horrific problems this might cause both of you if anyone found out hover on the edge of your exhausted consciousness, what it would do to your Dad even to know his darling Lucy had taken advantage of her own little brother this way. Tomorrow, you’ll think this through properly tomorrow. For now, you lay back on the bed, settling your head against your pillow with a warm satisfied sigh.

You’re tempted to leave Nick worshipping your balls, but he’s been so good he deserves better. You’re not even pissed off about your apartment anymore, just like always he’s way too cute to stay annoyed at. With the hand in his hair, you gently tug him up from between you legs, guiding his soft, wriggling body over your own until he’s resting his head against your boobs. He raises his head, staring up at you with soft, adoring eyes. It can’t be wrong, you tell yourself as you smile tenderly down at him. Not when he loves you this much.

With that lovely thought filling you up with warmth, you lie back against your pillow and slip away moments later into a deep and very satisfying sleep. Nick slumps against your slumbering body with his own cute yawn, nuzzling into your boobs as his eyes flutter shut. Soon, he’s sleeping too, brother and sister naked and entwined.