It wasn't that his children didn't need watchers. It was just The King couldn't find any that would stay to watch them. And, it is easier to build strong children than to repair broken men.
Chapter five of the prompt, the way you said "I love you," over a bottle of beer.
Another meeting. Another day that was being disrupted.
Lucifer looked down. It was the sound of two servants pushing scraping rock with all their might across the floor that made him look towards them; as a statue that dwarfed everyone in the room was being slid across the floor, the horrid scratching- scraping sound echoed through the large room, bouncing off the ceiling. It was one of his Commandments, the Commandment of Truth, grinding against the marble floor as his gigantic form slid from behind the ornate doors towards the king's throne. Half way there one of his legs gets snagged on the carpet, almost tumbling over as the women panic at the thought of breaking one of the strongest demons of the kingdom into tiny shards of rock on the floor. The sound of the grinding stone goes on and on as no one speaks, the large group of disheveled men and women huddled to the side, another group walking slowly behind the moving statue- until finally the servants, utterly exhausted, place the stone form of a roaring six armed two headed demon Commandment at the bottom of the King's feet.
The now, once feared demon turned into an ornament- is holding a squished hotdog, also turned to stone between his fists.
The group of children waiting for his attention look awful. Some were swaying side to side, faces red, pieces missing, one blue demon soaked and feathers dripping all over the floor, another shaking an empty bottle with great sadness, and many of them were leaning against each other- to keep standing.
And there in front them, was Meliodas. Unrepentant, like the leader of the group he was; with his hair disheveled, soaked to the bone, and dozens of red lipstick kisses over his face and skin and clothes smelling strongly of liquor. His usual expressionless face instead extremely grumpy.
"Is a hotdog a sandwich?"
The Demon King brow twitches, the hand under his chin clenching slightly as he stares at his son.
"Pardon?"
Meliodas scowls, the young boy's face scrunching up as he waved his arms around. Far more animated as a drunk then the usual prince.
"Is a hot dog…" he sneezes, glaring at his own body in disgust, before grabbing a small napkin Gowther hands him, "... a sandwich?"
Lucifer looks upon his son, then the crying defeated babysitter behind the group of nine children, and his now dead Commandment.
Meliodas kept talking, blowing his nose into the hankie.
"We were seeing if we could drown in a barrel of booze, so's we were throwing the lid back on and didn't let Mortician-" Here the blue demon behind him shrieked loudly, her wet feathers puffing up as she hissed- "there out' ands there was a lot of struggling, tons of bullshit, and then this asshole-" he points loosely at the general direction of the statue.
"The Commandment of Truth, my general Balam?" The King asked.
"Yes, that asshole-" meliodas sneezed again, "'h'wanted the barrel." Meliodas glared at the dead man, "it was mine."
His greatest warrior- his scariest fiend. His spawn of a child killed someone who could murder him with a flick, with a trick question?
Is a hot dog a sandwich?
"And what," Lucifer tapped his finger once upon his throne, "did he say?"
"Dont r'ember" Meliodas mumbles, before he suddenly perks up, eagerly waving behind him at the crying babysitter, that still was carrying the barrel. "Can we keep it? We gotta know if we can drown to death in booze. Because it's poisonous right? But- but were demons, and demons are immune to poisons, right? So can I drown in a booze barrel, or will we breathe in a booze barrel?"
There is a moment of silence, soft crying in the back ground, before the King waves a hand.
"Bring me Appollabrex, tell him he has been given the honor of being a Commandment. And tell him I have a question to ask him."