This is really lovely, Ben. Thank you for sharing your grief, the ups and downs of being an only child. First, I want to say that I completely hear and respect everything you said, and how you're feeling.
And ... nothing is perfect. Having siblings might be fabulous, "could" be fabulous - and it can also be absolute hell. You never know what you'll get. An abusive, violent brother like I had, or a special needs sibling who needs most of your parents' time, energy and financial resources, a sibling who can't figure you out and vice versa so you're not close and the gap widens in adulthood ...
But I get it - having what we perceive as a normal, loving relationship with a sibling would be wonderful and I'm sorry you haven't had, and won't have that experience. It sucks.
As for being away somewhere doing your own thing when bad stuff happens to your parents ... that could happen when you're 5 years old. People can be gone suddenly with no warning. We can't hover around our loved ones, afraid to leave their sides in case something happens while we're going.
Don't let fear stop you from living your life. Make the most of it while you can. It might be weird to imagine having kids, but if you can do it, imagine if you'd want them to stick close and be afraid to go off and explore and have adventures because they fear what might happen to you.
I'm sure your parents don't want that for you either.
Hm. I posted a story today about a reading I did several years ago (including the not-great-quality video) about a woman whose mother came through in spirit with pretty much the same kind of message.
Thanks for sharing this. It was eye-opening, as I'm not an only child, although I always wished I was because my brother was such a hateful, abusive moron and my parents never protected me from him.