No - always perplexed by the argument of sharing the burden when older, having someone to rely on etc. My brother and I have never fallen out, we speak probably 5 min per month. He has not visited my house in 3 years (despite invites). I have friends I can rely on much much more.
Cant say I would miss him in the caring for my elderly and ill mum and dad, nothing that wouldn't be sortable. Most caring of elderly parents ends up with one child regardless of the amount of siblings - at least if theres no expectation of other people picking up theres no disappointment.
When anything happens, i'll be looking to my DH and close friends for support, I imagine that my conversations with my brother will be limited to practical things. As ive said no big fall out, we have nothing against each other, just v different people.
I think sibling relationships are often romanticised on places like facebook #bestfriendsforever/sisterlylove etc. Yes some grow up close, but most siblings I know have a very practical and cordial relationship rather than relying on each other for everything (although most people I know have moved away from home towns).
Like anything - theres advantages and disadvantages of lots of situations, there are quite a few onlies in DS's class, all very well rounded, caring kids. They are as individual as any of their classmates with siblings