As I wrote before, typing the other members of my family was quite easy: My mother is INFP and my brother ISTJ. But my father was quite enigmatic and I couldn't pin him down, because he showed traits of ISTJ and INTJ at the same time, like the disregard for rules and at the same time constantly asking other people for help while I as an INTJ like to figure out these things by myself. Because he frequently terrorised my mother with clear-up attacks like "whom is this? Take it with you!" and the state of chaos our home was which caused a lot of tension I never doubted that he was an J. He clearly is an Introvert as well as a Thinker without much emotional reactions. The crucial insight I got after I read this about INTPs at introspektivblog.wordpress.com: "we put something away, and after two days it gets invisible for us".
Shortly after that, i found a box in the hallway containing parts for two different customers and a letter. Obviously, he meant to make the appointments to apply these parts and throw the letter in, but simply forgot these and the letter and stopped caring for these tasks. I should also mention that while he was quite successful in managing the business because he is still the best salesman because of his versatility, at the same time he can drop everything and follow his hobbies if the weather is inviting, not caring what happens while he is away. The importancy of things is directly related to the distance to his nose and that can be fatal. If he is in vacation, he is able to be unreachable at the one day, the few hours where his project gets fitted and he should be on standby for questions because of a somewhat sloppy preparation where the written information is incomplete. But no, if it is out of sight, it is also out of mind. I also couldn't get him to use ToDo-Lists systematically, because it was too much for him to set them up in the first place and obviously don't have that fear of failures most Judging types have. That leads also to the fact that long-term improvements with no urgency simply weren't made because they are usually not important at the moment.
While leaving me with the work while following his hobbies, he would often tell: "Today the weather is good, so I'm out - tomorrow it is going to be worse" (tomorrow means a sunday or so and implying to me that he will do the work on that day - but usually he doesn't show up). Same with the promises "I will help you" - either he simply "lack the time" or we will start together, abandoning me half the way down. So, it is also a story of broken promises. The laser-like focus on the end goals with is typically for INTJs is clearly not his thing. Another point was - the logical extension of broken promises - that you couldn't be entirely sure that he defended our position in negotiations. It happened more than once that he suddenly switched sides and stabbed you in the back, openly. Normally, you would call a break and realign the position of your side if you are convinced by the other side's argument. But openly stab your teammates in the back? Impossible for a lot of types.
To keep it short: He is a P, ISTP (the Virtuoso) to be precise - and the description fits. As a model-maker since his youth, he build a lot with very different materials. He started to build a steam powered locomotive in 1:11 scale - and that was it: he started. He quickly hopped to another projects when problems arised so at one time I had to clear out seven (!) projects out of our shared workshop to make room for the one I wanted to do while he was - at vacation. I would go crazy with that many open projects.
The type description is also true for his other hobbies: Yes, he did different sports: in his thirties, he did windsurfing, then he switched to sailing boat and started road biking. In his sixties, he even started skiing(!) - and he has a natural ability for kinesthetic which I learned when I went rock climbing with him. In short, he did a route on the first attempt without ever having climbed before which took me a few tries. That he is never one to be fully trusted - if something else fetched his interest or circumstances changed, old promises didn't count - is also very typical for ISTPs. That was also the cause for the failing of his marriage with my mother: after she declared she couldn't go sailing with him for months, he took the first occasion (fortunately this was not until 25 years of marriage) to switch her out for someone who did. He declared he doesn't really know what love is, for him the roll in the sheets is much more important. Everything fits with ISTP ... and if you look at the description, you have exactly that kind of enigma he displays: sometimes prioritizing, then suddenly switching interest, going with the flow now and ignoring it entirely the next day, very adaptable to different types of customers and very stubborn and insensitive, everything at the same time.
As a conclusion: On the one hand I am glad to have him as my father, because he allowed me to develop my handiwork and sports skills (because he tried to pull us into his hobbies too) and also didn't set boundaries with which I surely would have collided. On the other hand, he lost his sense of obligation to the company to a big part after he transferred it to me. Sure, he is still working and we switched positions - now he is the jack for all tasks - but he don't want to be involved in all the long-term planning like the refit of the shop (but is not shy to criticize something now and calling it a good idea after it is finished). And if he has scheduled a vacation, he doesn't think what those who stay behind have to endure which is totally the opposite of my INFP mother. And - like said box with parts - I have to clean up the mess he left behind. The same was also true with the locomotive - beginning with the day I started working on it, he never lifted a hand again for it, abandoned it completely while on the other hand I would have appreciated sharing that project.
And one last word about P-P relationships: strange things can happen. While a J would kick someone out immediately and never speak again with a cheater, among two Ps it can be quite different. Because they don't commit to a final decision, it can become zombie-like. INFP mother had this two times: she didn't broke up with ISTP cheater, even if she never condoned it and it took several years of distancing. But even now, they can work together without ill will. The next try with an ENTP showed the same pattern: other circumstances prohibited it to develop to a real relationship, but it stayed in that undead state for years where everything is still possible on the one side and realistically without a future on the other. Much like Schroedingers Cat: neither P will lift the lid to decide if the cat is alive or not.