I know this thread is old AF, but I just wanted to put in my two cents.
INFP female here, I've had a great number of interactions and close ties with male ISTPs. First of all, my mom is an ENFP and her high school sweetheart was an ISTP. They were separated for about 10-15 years and had their own families, then reconnected in their 30s and got married, and had my little brother, who is also an ISTP. I also dated an ISTP on and off for a few years, and I had a work friend who was a male ISTP as well.
With my stepdad, the dynamic was interesting because he had BPD, and therefore never had any desire to have a relationship with me. He was actually kind of emotionally abusive, and was extremely insensitive to both me and my mother. Unsurprisingly, they divorced a few years ago, but the dynamic between them actually worked really well when he was mentally stable and on medication. He was a blast to be around as long as he wasn't having an episode.
Like I said, they gave birth to my little brother who is also an ISTP (basically a reincarnate of his father, but luckily seems to be lacking in BPD). My little brother is the apple of my eye and I love him to death. We fought a lot growing up, but now that we're older we have an amazing bond. He adores me a lot, even if he doesn't really show it too much.
The romantic relationship with the male ISTP was interesting to say the least. He was an addict, and I met him when he was 2 years sober. The relationship started really spontaneously and passionately, and I got really attached to him, and he was attached at first as well. However, as time went on he got steadily less and less interested in me, and eventually became insensitive, condescending, and demeaning, and inevitably ghosted on me. He later apologized for this behavior, but.. I'm not surprised as ISTPs are usually insensitive AF.
I've seen a weird pattern with ISTPs having a fondness for military history, I guess it must be their Ti being into the intricacies of military tactics, and their Se liking the thrill of it all. For a while I thought the ISTP I dated had to be an iNtuitive because he wanted to teach history, but then I remembered my ISTP stepdad was OBSESSED with military history, too.
The cool thing about comparing ISTPs with INTPs is you can see the difference in the way their inferior Fe comes out. I've noticed their Ti works pretty similarly, however ISTPs tend to be way more blunt and crass due to their Se kind of making them say what they feel whenever they feel like it, regardless of social consequences. In my view, ISTPs' inferior Fe comes across as insensitive to other's emotions, social "rules", and blatant disregard for human emotion; whereas INTPs' inferior Fe comes across as not dealing with people or social situations well, general social awkwardness, lack of charisma, etc.
I say all of this with love as I adore most IxTPs but those are just my observations.
