Sibling Trust

I was almost ten years old the very first time I showed my vagina to my teenaged brother in exchange to his showing he how boys rubbed their penis. He had sort of talked me into it and I reluctantly did it but watching him doing it actually fascinated me. I did get a little grossed out that first time when he ejaculated but since none of it got on me I dressed quickly and left his room while he cleaned up. That night I masturbated in my room thinking about what we had done.
He and I did repeat our sex play very sporadically up until I had my first period at thirteen as our parents had to be out of the house to provide the privacy needed but as soon as they did go out we'd do it. My brother and I never engaged in sex but we did masturbate together when we could do it safely without getting caught. Though now as adults we do not engage in any sexual behavior with each other, we have both found that our sex play history has oddly brought us to trust each other deeply.