This. ^
I have very little contact with my one brother and DH has very little with his. They live in other countries. No rift. Just drifted apart over about a decade and a half. I barely know my 2 nephews (both mid to late teens now.) DH barely knows his niece. Contact is infrequent and rare. Last saw any of them 5 or 6 years ago.
I know many people who have siblings who they have NO relationship with at all, sometimes there is a rift, sometimes it's coz they live 100s or 1000s of miles away.
As for the comments about 'it's so hard for an 'only' when the parents become elderly/infirm,' in MOST families, it's the FEMALE who ends up doing everything anyway, and in cases where there is more than one female, the oldest is usually the carer/fetcher and carrier for the parents. Often whilst holding down a job, looking after kids still at home, and sometimes looking after grandchildren too.
It is a myth that people with a sibling/multiple siblings will have a great easy ride in life, lots of help with their parents when they grow very old, and a lovely Waltons-type relationship. It just doesn't happen. Not for the vast majority of people. Even in the families where they LOOK like a lovely, cosy, family-is-everything lot, there's a 90% chance one half secretly hates the other half.
I am sorry you feel blue about being an 'only' @Itsjustmeonmyown but as the poster I quoted said, your beliefs are a fantasy.