"F-F-Ferb what are you doing?!" Phineas asked, his voices pitch raising in panic.
Ferb hushed him gently before capturing the redheads soft lips with his own. Phineas froze in shock and his hands slowly snaked up Ferbs body, one remaining on his back, the other cupping the back of his neck, both desperately pulling him closer.
Ferb chuckled softly to himself and allowed his hands to begin unbuttoning Phineas' shirt. Once the shirt was unbuttoned he used one hand to hold them up, the other lifted Phineas. Phineas moved his arms to allow his shirt to fall off, before returning them to their previous positions. Ferb brushed the shirt away and allowed Phineas to fall back onto the bed.
Phineas stared up at him red faced and panting, his bewilderment clear in his eyes.
"F-Ferb?" he squeaked
Ferb grinned at his brother, licking his lips slowly and watched with satisfaction as Phineas' eyes followed his tongues movements and he gulped heavily.
Phineas' chest was rising and falling rapidly, and Ferb grinned. Reaching over to a table he grabbed a pair of fuzzy pink handcuffs and tied Phineas' hands so the headboard.
The redhead squeaked in bewilderment as Ferb leaned down, kissing him softly. Phineas squeaked again, and Ferb pulled away slightly, instead leaning up and capturing his ear lobe in his teeth. Phineas gasped and Ferb sucked on it softly, grazing his teeth against it. Phineas moaned softly and Ferb grinned as he kissed back down to Phineas' lips. He paused to give the redhead a quick kiss before continuing in his path down to the redheads nipple. Phineas stared down at him in shock and Ferb grinned, taking the bud between his teeth. Phineas gasped and his body arched to Ferbs touch. Ferb swirled his tongue around the bud, grinning St the sounds Phineas was making. He nipped it gently and Phineas moaned, arching his back and exposing miles of creamy skin. Ferb leaned forward eagerly, nipping and sucking on the soft unmarked skin. Phineas moaned softly, and Ferb reached down and tweaked his nipples between his fingers. A loud gasp and a softer moan escaped the redhead. Ferb removed his lips from Phineas' neck, grinning in satisfaction at the throbbing red hickey he had left.
Looking behind him he grinned when he noticed the tent in Phineas' pajama pants. He shifted himself down, and removed the garment. Phineas' cheeks turned a darker red in embarrassment and Ferb looked at him, wiggling his eyebrows. He looked back down and shifted once again before grabbing Phineas' rock hard erection. A loud gasp escaped Phineas and he bit his lip furiously to silence himself. Ferb began pumping his hand up and down Phineas' member and the redhead writhed beneath him, soft moans and squeaks escaping him despite his attempts to keep them inside.
Ferb shifted once again while Phineas' eyes were closed and replaced his hand with his mouth. A loud gasp escaped Phineas, and he looked down at Ferb in bewilderment. Ferb ignored him, focusing on sucking on his brother. A loud cry escaped Phineas, and he shivered.
"F-Ferb" he panted "S-Stop" he desperately held back a moan "S-Stop I'm gonna- ahhh" he released a loud cry as he climaxed into his brothers mouth. Ferb swallowed and grinned, licking his lips as he crawled back up Phineas' body.
"I'm sorry" the redhead whispered
Ferb shook his head
"I'm not"
He sealed his lips to Phineas' and Phineas desperately struggled against his handcuffs, desperate to caress Ferb, to feel him in his arms.
"Ferb please uncuff me" he panted "please"
Ferb grinned at him
"why?"
"Pl-Please" the redhead panted
"mmm, why?"
"I want to feel you, to caress you" he tugged against the restraints "p-please"
Ferb grinned, grabbing the key he slowly reached up and unclipped one of Phineas' wrists. As soon as the second one was unclipped Phineas lurched up and pushed Ferb back onto the bed, sealing their lips together desperately. His hands had a mind of their own as they snaked down Ferbs body and unbuttoned his pants. His pants and boxers were yanked down all in one fluid motion, and he kicked them off the rest of the way, all the while desperately caressing every part of Phineas he could reach.
Phineas pushed their hips together and a weak moan escaped the Brit, as he arched his back and dug his fingers into the bed.
"Ph-Phineas-" Ferb moaned weakly "le-let me up"
Phineas leaned forward and kissed him again, slowly releasing his hold on the Brit.Ferb immediately flipped him over and stared down at Phineas with his magnetic blue eyes. Phineas he gulped heavily and didn't realize he had spread his legs until Ferb chuckled and wiggled his eyebrows. Phineas' cheeks turned a furious red, and he grinned sheepishly. Ferb braced himself however, and when Phineas nodded he pushed into him.
Phineas grunted, digging his fingers into the bed as his body adjusted to the feeling.
Once his body has adjusted he nodded at Ferb to continue.
Ferb complied and Phineas released a weak moan.

"Hey mom?" Candace asked
"yes Candace?"
"do you hear something?"
no I d-" she stopped speaking when she heard a loud moan. Her face turned white and she nodded "yes. Yes I do"
"do you think Phineas is... you know?"
"Maybe.... Probably... I dont know of anyone he could be having sex wit-"
"oh god Ferb!" came a loud cry "I-Im gonna- ahhh!" a loud moan echoed around the house, and Candace and Linda exchanged a glance before fainting.