Dear Rico,
Sounds like there have been some struggles in your family but that they have bonded you and your siblings. I have heard a variety of answers to your question about how we came to have the family we have here in mortality. For sure, Father is guiding this. We chose our parents before we come. I have a feeling that some of us were essentially in the same relationship with our family members in the pre-existence as we are here in mortality. For each meeting, there is a purpose. I look at my own children, at their relationship with each other.... it is different from my relationship with my siblings. Fortunately the relationship that my own children have with their siblings is very close, supportive and caring. My sisters and I are a touch-base every once in a while sort of relationship. I wish on you the kind of relationship with your brothers and sisters as my own children have.
And no question is a 'stupid question'. There are probably many who wonder this same thing, and are glad you asked. I hope that someone else will also reply with a more in depth and detailed response. There is a lot of knowledge in the collective here.
And yes, in the temple you will learn more about your purpose and your understanding of the plan of salvation, to include pre-existence, mortality and our destiny will become more clear.
Will you be able to go to the temple soon?
Angie