"I don't understand how this happened! The first time we three had sex, you told Rose Time Lords weren't compatible with humans!"
"We're not. But your implant's... well, not exactly standard human hardware, is it? Can accommodate more differences in DNA than Rose."
"But I had it set to sterile!"
"Yeah. And the chemicals that setting makes it produce are suitable to kill off the sperm of any known species."
"Exactly! So why—"
"Any known species."
"Oh." Jack looked at the beeping line on the medical scanner. He took a deep breath and put a hand over his belly. "Just so you know, I'm keeping it."
The Doctor covered Jack's hand with his own, cool and firm. He wrapped his other arm around Jack's shoulders and pulled him close. "I'm the last of my species, Jack," he whispered into his hair. "I was ready to beg you to."
Jack turned his head and softly kissed the Doctor's mouth. "You have to promise me one thing, though."
Jack grinned. "You have to be the one to tell Jackie."