Bowser was in his room with his three sons, Larry, Iggy and Lemmy. The boys were sitting on the bed while their father stood up with his foot raised and planted on the bed. He was actually teaching his sons about the fun of masturbating. Somehow, the day ended up like this...
"Now then, let's start." Bowser reached down to grope at himself. He played with his fat nut sack, which was a darker yellow than the rest of his skin. His floppy and cut member slowly erects into ten inches of fat daddy cock, that was slightly pressed on the underside of his just as fatherly and chubby gut.
Larry, Iggy and Lemmy stared at their father's penis: their eyes seemed to grow wide alongside with the speed of Bowser's dick erecting. When it reached maximum stiffness, they blinked and suddenly felt hot all over. Seeing it erect was so fun that they two grew erect. Their little three inches of koopaling dick was out and made them all put their hands between their crossed legs to try to hide their member.
Bowser started to stroke himself slowly, "You boys comfy? Then let's begin!" The proud father wasn't shy at all as he rubbed himself.
Iggy stared at the fat head of Bowser's dick... and wanted to kiss it so much...
Lemmy was breathing through his nostrils, hoping to catch whiffs of his daddy's musk...
Larry swallowed the drool that quickly pooled in his mouth as he wondered what it'd feel like in his mouth as it throbbed...
"The trick is to savor it... unless you're just rubbing out a quick one." Bowser spoke as he tugged upward to squeeze his cock tip, which made a pre bead appear from his urethra. He shook his cock some and the pre bead dripped into a slimy string of pre.
The boys' eyes grew to that dripping. They followed the drip with their eyes and saw it snap finally after a few inches.
Bowser rolled his finger around his cock to smear the pre seed around it, "Pre cum is excellent to use as a lube!" He chuckled some before resuming his masturbation. 
Larry swallowed a lump in his throat before he finally spoke, "Hey Dad?"
Iggy and Lemmy quickly held up a finger to their lips, "SSH!!"
Bowser chuckled, "No, let your brother speak. Yes, son?"
"What do you think about when you're... doing that?"
"Well, I think of a various amount of things when I'm masturbating. But for today, I'm thinking of Birdo. I saw one bent over to pick some flowers earlier and their cute pink rump was out and presented. I didn't even see anything too explicit on her but seeing that smooth butt has stuck with me all day."
Larry asked, "But... you're a king. Can't you have them come here to rub you?"
Iggy spoke up, "Or won't you use magic to help?"
Lemmy added, "Or use magic to make a picture to look at?"
Bowser chuckled, "Yeah, yeah. I can easily bring one here, I can even make a fake one using magic or use powers to project an image of whatever... but there's something about using your imagination that's just as fine. Believe it or not, magic wasn't always available. Back in my younger days, that's all you had to use to get off. I'm not saying it's not healthy to look up naughty things, but don't think that's the only way to get off. Honestly, you boys are lucky to have technology to help. While you can look up some tail, I had to hope for a windy day to see some tail." He chuckled. "...but don't take my word too seriously and find everything sexy or relieve yourself too many times a day. You don't want sex to get stale."
The boys thought on that. Sure it sounded boring to them but they weren't completely turned off to the idea. Maybe they'd give it a shot one day.
"Mmmff~" Bowser breathed out through his nostrils as his rubbing speed increased. His head leaned back just as his free hand lifted to rub as his strong chest, "I'm gettin' close."
All three boys looked at their daddy's penis when he said that. The blush on their faces grew darker and their little tails wagged quickly. They sat there as quiet as they could to enjoy the soon to be sex class session their father generously gave them.
Suddenly Lemmy cupped his hands and held them near his father's cock.
"What are you doing?"
"I don't want dad to ruin his fresh bed sheets...! I'll catch his load!"
Iggy pushed himself next to Lemmy, "What?? Why do you get to do it?!" He cupped his hands and held them near Bowser's penis as well, "As if your tiny hands can catch all of dad's load!"
Larry scooted closer, "What about me?? I wanna help dad too!"
As the boys argued, Bowser paused his masturbation and looked annoyed as he stared at the ceiling and thought to himself, "My sons are arguing about this... they really do fight over anything." He smiled softly... then angered up as he looked at his children, "STOP!"
The boys quickly dropped their argument as they heard the bellow of their father.
"All three of you will catch my cum, Now behave!"
All three nodded together, "Yes dad..."
Bowser went back to masturbating. He closed his eyes and pictured Birdo's smooth bottom again... but now, his mind started to rush with other thoughts he preciously got off too: that one time he saw Yoshi napping with his legs spread to show off his smooth crotch... that one windy day when the wind blew Princess Peach's dress up to show her pink panties... "Here it comes, boys...!"
All three of them had their hands out and were shaking slightly from the excitement of catching their daddy's cum.
Bowser lets out a deep groan as it happened! Thick spurts of his cum ejected out and splashed over his own sons' hands and arms.
Iggy, Lemmy and Larry all sat up on their knees and leaned in to make sure to catch the big blast of daddy cum. They each gasped and stared with unblinking eyes at the amount of cum they were seeing. Their mouths were slight gapped and their little penises ached with how stiff they were.
Iggy smiled big time, "Wow, dad, you cum a lot...!"
Bowser exhaled heavily, "I've been holding that in for a few days now. It feels great to let it out finally!" He chuckled. 
Larry was playing with his dad's cum, admiring how sticky it was and how much he could make sticky strings with it.
Lemmy was seen masturbating furiously; he was using his father's cum as a lube.
Iggy gasped, "Hey! What happened to wanting to keep dad's sheets clean??"
Lemmy just giggled as he obviously lied earlier on that. He just wanted to always do this. "Oh c-come on! You're not hot after seeing that?? FEELING that?? Forget that, I'm too shaky to go back to my room!!"
Bowser chuckled, "It's fine, Iggy. If you boys wanna masturbate, go ahead! The lesson's over; you're on recess time now." 
Iggy huffed... and looked back to Iggy, who was still stroking himself quickly. The lewd sounds of his sticky hand rubbing his penis was heard. Next, he looked to Larry, who was in his own world as he was curious on the taste of his father's cum. He had his eyes closed and sucked his fingers clean of cum, all the time while jerking off  while also using his father cum as lube. Iggy looked down at his messy hands and arms... then lifted his hand to his face to sniff the goop. He used the scent to get off and followed his brothers' example as he too used some of Bowser's cum to jerk his penis with.
Bowser crossed his arms and smiled on the cute sight of his sons getting off. 
The boys were ready to pop at that point. There was no holding back or savoring the moment. It was at the same time that all three of them reached their orgasms: Lemmy spread his legs and his little few spurts of cum landed on the bed, Larry actually closed his legs and shivered as he came over his own thighs and finally Iggy pressed his sticky hand to his chest and came on the sheets between his legs and on the edge of the bed.
Bowser's tail swayed slowly as he felt an incredible warmth splashed over him. It wasn't the warm musky air of all four of them, but instead it was happiness on seeing his boys so pleased and happy. "You boys alright?"
All three of them flopped on the bed: Lemmy flopped forward with his butt in the air, Larry flopped backwards and Iggy flopped on his side. They all answered with a lazy, "Uh huh~"
"Good! Now, recess over, go clean my bedsheets."
That sparked a sudden burst of energy in the three boys as they each shot a look at their father, "Aww, what???"
Bowser arched an eyebrow at them, "What? You messed up my bed so clean it!"
The boys sighed as there was no use in arguing with their father. It's not that they hated doing what they were told; laundry was just never fun.
Iggy looked at Lemmy, "Wait, why are you sad? I thought you loved doing laundry?"
Lemmy tilted his head"...What do you mean?"
"You always sniff the clothes before dropping them in the wash."
Lemmy blushed big time, "NO I DON'T! ...and stop peeking at me doing laundry!" That was true as Lemmy would love to sniff his siblings underwear before tossing them into the wash. "Or I'll tell dad you wear Wendy's makeup and pretend to be a pretty princess!"
Iggy blushed brightly, "S-SHUT UP!!" This was also true: Iggy would wear high heels, a short dress and put on makeup to pretend he was a girl.
"That was you?" Bowser held his hand to his chin, "I thought Wendy was lying just to get me to buy her more makeup..."
Larry chuckled, "Guys, come on. It's nothing to be ashamed of. Everyone has their own kinks. Right dad?"
Bowser nodded, "Yep! Like Larry here using his wand as a vibrater!"
Larry blushed brightly, "DAD!!" Also true: one bored day, Bowser needed Larry for something and was about to enter the room when he noticed the door was cracked a bit. He looked in and saw his son on his back on his bed with the wand vibrating over his bits, taint and butthole. He decided to leave Larry alone that day and that image was stuck in his mind ever since. He was proud to know his sons were getting creative with their ways to get off. 
"What? You left the door cracked." Bowser winked and turned to leave, "I expect those sheets cleaned before dinner!"
The three boys was left there, red in the face from having their kinks revealed. One thing for sure, that would be one awkward time together as they gathered the dirty sheets to wash them together. But they were closer and this was just one more thing to overcome to be closer as a family.
-End