Across the land, millions of brothers and sisters look forward to their sibling's birthday – because there's a good chance they'll get a present out of it themselves.
The trend of the 'bonus birthday' is a growing one, according to a report, but there are fears it is conditioning children to only look after number one.
Parents who don't want their other children to feel left out on a sibling's big day splash out on gifts so that the occasion becomes a whole family celebration.
Researchers for OnePoll.com surveyed 2,000 parents and found almost half of children are having two or more 'birthdays' a year because parents buy them presents on their sibling's birthdays, as well as their own.
On top of that, instead of saving all the presents for the birthday boy or girl, grandparents and even family friends are getting in on the act and buying gifts for each child on family birthdays.
But for some, the gesture has backfired, with a fifth admitting their children now expect to receive a gift on every single birthday a brother or sister celebrates. (Guilty as charged: my kids now expect - and get - three a year. D'oh!).
A spokesman for OnePoll.com said: "It is astonishing to think that parents of today are more willing to spend extra money on children who aren't even celebrating a birthday, than teach them that on one day of the year it isn't all about them.
"We know that the majority of mums and dads will simply think they are being kind and thoughtful, but the fact is that children need to learn how important it is to think of others before themselves.
"And if that means allowing their brother or sister the limelight for one day of the year, then so be it.
"Modern children should be taught not to expect presents all the time, and should be able to sit nicely and enjoy the fact their sibling is so happy on their special day."
More on Parentdish: When is it time to stop the birthday parties?