-I'm an INTP. (Oldest child)
-My brother is an INFP. (Middle child)
-My sister is an ESTJ. (Youngest child)
-My mom is an ISFJ.
-My father is an ESTP.
Curiously, despite my sister being the youngest, she often comes off as the oldest due to her personality alone. She's more outgoing, confident, and tends to boss my brother around a lot. But she's usually not mean to him, she just takes the lead, and he follows her lead. Many people have assumed my brother is the youngest because of how he often follows what my sister tells him. The two are very close despite being opposite types (letter-wise, at least).
I get along with my INFP brother very well. We often seem to communicate very similarly, share lots of interests and hobbies, and have a similar outlook on life for the most part. Usually when I'm with him, I end up taking more of a "leader" position naturally as I'm the older sibling, but I do so less than my sister does.
With my ESTJ sister, we generally get along, but sometimes have conflicts due to personality clashes. Sometimes she tries to boss me around like she does to my INFP brother, and I hate being told what to do so I get frustrated and just want to do my own thing, which gets on her nerves as she doesn't understand why I don't just do what she believes is the most logical thing to do. Meanwhile, sometimes I admittedly am a bit too blunt towards her and that irritates her as well. But despite our personality clashes we can still get along well and have good conversations. With her, my conversations are more down-to-earth, more about life experiences, day to day stuff, etc. It feels as though I communicate with her more through Si, whereas with my brother our conversations feel heavily Ne oriented, if that makes sense.
My parents being ISFJ x ESTP is curious because it's often stated to be a very compatible type pairing, and while I don't think MBTI alone is responsible for it, the truth is that they seem like they were made for one another. They are often like opposites, but complement each other so well. They share a strong sense of mutual respect, and share the same values, principles, beliefs and world view. I think that's the main reason they're so compatible, but personality wise it really feels like they each excel at the things the other struggles with, and thus make a really great team. I honestly dream of one day finding a partner that makes just as good of a match with me as my parents do with each other.
I really enjoy talking to my mom, she's the one I talk to the most out of my two parents, as my father tends to be busier throughout the day. My mom often shares a lot about her own experiences, tells me what's on her mind, and I enjoy listening to her and learning from her. I've noticed that if there's something she really wants to talk about and my father isn't available, I'm often the next person she goes to talk to, not really because she wants me to help her with anything, but rather because she wants to talk to someone that will listen, and I seem to be pretty good at that. But I also learn a lot from her, and I've always said that she's played a major role in helping me develop my Si and Fe to the extent I have them developed currently. Just the experiences of talking to her, understanding how she thinks, behaves and reacts to different things has given me a lot of insight, and I've learned quite a lot of things from her. She may also be the main reason why I find it easier to connect with and understand xxFJs in general than other INTPs I've seen.
My ESTP father tends to act not only as my father, but also is my boss and my mentor. I help him with the family business, so he assigns me work and is training me so I can one day take over for him when the time comes. He is also my mentor in terms of understanding life in general. He tries to guide me to become a responsible and functional adult. Admittedly sometimes we have some clashes because he gets a bit frustrated that I can sometimes come off as oblivious to my surroundings and have a hard time reading small cues that he finds second nature to him (He's an Se dom, whereas Se is my blindspot, so I can see why I struggle so much in certain areas that feel extremely natural to him). Despite our differences, I know he really cares about me and is doing his best to ensure I grow up to be a responsible and mature adult like he is. Plus, he's also pretty affectionate and likes to occasionally buy us things we like and tell us how much he loves me and my siblings.
Oh yeah, and people often say I'm a lot like my father, which is curious since personality wise we're pretty different, but one thing we share in common is a very sharp mind. We're very fast to understand new information and learn new things, and we tend to be knowledgeable on many topics, so many people around me often say I'm like my father in that way.