Yay! It's called What sister! Well, Jack's a father. So what'll he be like?
Jack invited Gwen and Owen over to his flat. He dealt with aliens countless times before, but now, he faced a new, more difficult monster: twins.
Ianto let them in. "He's in his other bedroom; the twins are staying there... He's treating it like a military operation."
Slowly, Jack crept in from the other room. "The enemies are asleep."
Gwen sighed. "Jack, it's just babies. There's no need to act like they'll kill us. They're probably adorable."
"So are some aliens," he crawled over.
"Okay, calm down," Owen held his arm out to get Jack to stop. "Now you're just overreacting. They're not going to murder us."
"You haven't seen them, Owen! Believe me; I'll show you when they wake up... Which won't be that long."
It wasn't that long, really. Only an hour later, crying started from the other room. Everyone looked at Jack. "Your cue," Ianto told him.
"I know it is," he sighed and went to get them.
A minute later, he was back in with the twins in both of his arms.
"Alright, this is Linda," he lifted up his right arm a bit. "And Star," he lifted his right.
"I knew they'd be cute! What makes you think they're going to murder us?" Gwen laughed.
Star pushed herself up a bit. The room was perfectly quiet, so why not make a bit of noise? "TAR'IS! TAR'IS!" She shrilled.
"... Yeah, they're a bit homesick."