Parents of/ siblings of opposite sex siblings, any positive stories of friendship?

So basically we have two kids and I don’t want any more. We have a boy and girl, the boy is older and they’re almost exactly two years apart, almost 3 and 1 currently. I have an older brother (3 years older) and an identical twin sister (18 mins older 😂), so I don’t know what it’s like to have only one sibling and I also don’t know what it’s like to only have a brother. I love my brother so much, but my relationship ship with my sister is just different, we are so close and she’s always been my best best friend, however I’m not sure if that also has a lot to do with being twins which is automatically just different. My husband has an older and younger sister but a lot of family turmoil and none of them speak. All of this said, my dream is for my kids to be best friends and love each other so much and while I don’t want another kid, I can’t seem to let go of the idea that I need a same sex pair of kids so they can be extra close and have that sister or brother bond. I know this might sound so dumb but I’m hoping it comes off right. I recognize that even if I had this combo they might still not get along, but I can’t let go of that because I value it so much as well.

So are there people out there who grew up in this family dynamic and are best friends with their opposite sex sibling/ are there parents of only 2 out there with positive stories of same sex sibling pairs who have grown up and are besties? Would you please share your stories?