Disclaimers, etc: see part one.
An Eighth Doctor/Rose Story
Chapter 8—Jack's Jealousy
Jack told Rose the truth. John had been a Time Lord, just like The Doctor. And just like The Doctor, John had a grip on Rose that Jack could not loose. Because of a Time Lord's threat looming over him, he had not pursued Rose as he had wanted. Instead, he supported her in many other ways he had not practiced in years. Life had been easier when he was willing to shag any organism, but it was too strange not being able to be with Rose in the same way. It was not that Jack feared for his life (but he really should), but it was that Jack did not want to cause a rift between Rose and The Doctor. He would not care what would happen to their relationship if he had gotten together with Rose, but Jack felt obligated not to cause Rose to hate The Doctor for his actions against Jack. Jealousy again.
Now they both had a united front. Both Jack and The Doctor could be jealous of John. Moreover, The Doctor would be livid for believing he was the last Time Lord. Was it possible that John had simply been visiting Earth? Or was John already dead with the others, only existing at this one time because he had visited Earth in this year before the destruction of his home planet? When John left in his TARDIS, was he unknowingly seeking oblivion with his kin? Where would Rose fit into this?
Jack felt a presence wash over his mind. He examined it all he could, finally identifying the intelligence as the TARDIS.
"I know girl," he said, "we all want the best for her." He had said it low enough so that Rose could not hear it. Although they had just walked into the TARDIS, he knew that the TARDIS had already read the impression of his thoughts as if they had been speaking for hours. It wasn't possible that she didn't know of his feelings for Rose, just like it wasn't possible that she hadn't found out about John.
Jack leaned against the walls of the TARDIS and asked her in a tongue he asked not to be translated to Rose, "Is it true he is another Time Lord? Or is he simply here to die? If that's the case, I can't let him be with Rose. The Doctor be damned and let him kill me, but I will be with Rose before I let her love a Time Lord that will be sent to his death."