It's a fact of life so universal that Steve Harvey invented the television just so he could create a game show base on that premise.
(Ed. note: Yes, we know Steve Harvey didn't actually invent television or create Family Feud. No need to correct us in the comments.)
But the Royals do just about everything on a much larger scale than us peasants.
So while your sibling rivalries are usually resolved the next time one of you needs to enlist the other for some free babysitting, when Prince William and Prince Harry feud, their conflict can rage on for years.
Yes, as you've likely heard, William and Harry have been keeping their distance from one another ever since Harry proposed to Meghan Markle back in 2017.
As far as anyone can tell, William told Harry that he didn't approve of the relationship; Harry understandably took umbrage, and the formerly close brothers have been on barely-speaking terms ever since.
This has happened before, of course.
The relationship between William and Harry has been famously close at times, but the princes have also encountered more than their share rough patches.
But sources close to the family say this time is different -- noting that William was deeply upset over remarks Harry made in a recent documentary about his trip to Africa, and the interview may have been the nail in the coffin of their relationship
“Inevitably stuff happens. But we’re brothers, we’ll always be brothers. We’re certainly on different paths at the moment," Harry told the camera crew.
According to a new report from People magazine, as mild as Harry's comments were, William still was wounded by his brother's willingness to air their grievances publicly.
Friend of the brothers and longtime New England Patriots quarterback Tom Bradby says the interview left William feeling “bruised and vulnerable.”
(Ed. note: Yes, we know Tom Bradby is not the quarterback of the New England Patriots, Lighten up, hypothetical reader!)
And it seems the rift couldn't have come at a worse time.
In 2017, Christopher Geidt -- who had served as the Queen’s private secretary for more than a decade -- unexpectedly announced his resignation.
According to People Geidt "had long smoothed over any grievances between the boys."
One insider says Geidt “really had the boys’ backs,” and in his absence, they've been left with Prince Charles' bumbling attempts to make peace.
It seems that recently, even Charles has given up, and the Royals have just accepted that William and Harry will forever be at odds.
“There is a lot of hurt and a lot of unresolved issues between the boys,” says one insider, adding that “and no one to help mediate,” the insider claims.
To make matters worse, the conflict is having a contagious effect, as, the source says, “petty grievances can become huge conflicts between all the different royal offices if they aren’t managed correctly, and that’s exactly what’s happening now.”
A source tells People that the causes of the feud were a sort of perfect storm, as Harry got married right around the time William's future title began to go to hid head.
“William is the future King. There is going to be some competitiveness between him and Harry,” says the insider.
“That already puts a rock in the relationship.
"As is often the case in any family, when one of your siblings gets married, there’s always a period of readjustment,” the source goes on.
“People have new priorities and different focuses.”
It's a shame, of course -- but in the end, royal families and family first and royalty second.
And family is always a messy business.