Jacen’s got more Force power than Jaina, and Jaina trained five weeks with Mandos

“You’re welcome,” Mirta said. “Now, the thing you need to know about your brother … he underestimates you.”
“That’s not really news, Mirta,” Jaina said. “Maybe not even true. He’s magnitudes stronger than me in the Force. All I’ve got on him is five weeks of Mandalorian commando training.”
“And that’s enough to get the job done.” Mirta’s tone was reprimanding, like a parent scolding a child for wanting a third bowl of frezgel. “But I mean, his weakness is more delusional. He’s convinced you couldn’t have taken his arm—at least not alone. He thinks Luke was with us.”
Jaina paused, recalling Caedus’s confusion at the end of the battle. She also recalled her own condition, how the strange surge in her Force powers had suddenly faded just before Caedus had redirected the stormtroopers’ fire. “Maybe Luke was there.”
Mirta shook her head. “He wasn’t. I was conscious most of the time—and I didn’t see him.” She waved the blaster muzzle at the door. “Now get out of here. You’ve only got an hour before my next meds are due—and no offense, but I don’t want you as a roommate.”
- Legacy of the Force: Invincible