At 55 my ISTP mom-in-law uses so much Fe, I was avoiding her. She made me want to unleash Te hellfire upon her...
At 33 my ISTP ex shows massive Fe towards his kids and me or the few others he cares about. For him it is simple but strong when it happens.
Fi scares the shit out of him though. He is very wary of it.
haha, little ISTPs, one day you will also be sweet