Sirius was tired. It was not easy running after two kids, hyped up on sugar no less, to try to get them to sleep. Of course Remus didn't help. He was the one who had fed the kids all the sweets and chocolates they wanted simply because Remus couldn't say "no" to them. Even Sirius had trouble saying "no" to his kids when they approached him with the deadliest weapon kids possessed against parents: the sad puppy eyes.
But the thing is that Sirius had grown up with Regulus, who was a master in that particular attack. So Sirius succeeded in saying "no". But the problem was Remus. As soon as Sirius said no, the kids would run to Moony with their demands. And Moony being the big softie that he is [although he would deny being a softie quite vehemently with a smirk on his face] would give them whatever they wanted.
Sirius sighed as he got up from his chair. He had tucked the kids in their beds half an hour ago before returning to his study for some work. But sleep was pulling him and the thought of curling up with Moony was too sweet to resist. And so with a smile on his face and a skip in his step, he made his way to Moony and his bedroom.
As soon as he opened the door, Moony looked up from his book and smiled sheepishly at Sirius. For right next to him slept their son Harry while their daughter Rose was curled up in Moony's lap.
He looked at Moony.
"They came in five minutes after you tucked them in their beds saying they wanted to sleep with us tonight."
Sirius raised an eyebrow.
Moony smiled at him and said, "I couldn't say no to them."
Sirius chuckled as he climbed into bed with his husband and kids. He helped Remus to settle a sleeping Rose in between them, right in between Harry and Moony.
He leaned forward, careful not to wake the kids, and softly kissed Moony on his lips.
"I know you couldn't."