Venus Williams was the first of the Williams sisters to make a splash in professional tennis. But Richard Williams, their father, was always convinced that Serena — 15 months younger than Venus, and the youngest of Oracene Price’s five daughters — would go on to have the better career.
Richard Williams was right. While Venus has enjoyed a magnificent career, winning seven Grand Slam singles titles, Serena has won 23 Grand Slams and is widely acclaimed as the best female tennis player (maybe the best tennis player of any gender) of all time. What was true of the Williams sisters — that the younger one went on to be the better athlete — is also true across sports generally. This is the “little sibling effect,” one of the most intriguing findings in sports science: Younger siblings have a significantly higher chance of becoming elite athletes, as University of Utah professor Mark Williams and I explore in our new book, “The Best: How Elite Athletes Are Made.”
The effect was demonstrated in a comprehensive analysis of 33 sports in Canada and Australia. The study compared elite athletes — who had reached senior international competition — with near-elite athletes, who had reached the junior international or senior domestic level. One finding: “Elite athletes were more likely to be later-born children.”
On average, the two groups had the same number of total siblings. What mattered was whether those siblings were younger or older. The elite athletes had 1.04 older siblings on average; nonelite athletes had only 0.61.
Younger siblings’ advantage appears among both male and female athletes, according to that study, and other research found additional evidence of it in women’s sports. A 2014 study of the athletes vying for a spot on the U.S. women’s national soccer team, covering players involved in national team training camps, found that around three-quarters of players had an older sibling; only 20 percent were the oldest child, and just 5 percent were only children. National stars Megan Rapinoe, Mia Hamm and Alex Morgan were among those who played soccer with their older siblings as children.
Even when two siblings both reach professional status, the younger one tends to be more successful. A 2010 study by Frank Sulloway and Richard Zweigenhaft of 700 pairs of brothers who played Major League Baseball found that younger brothers were 2.5 times as likely as their older brothers to record superior career batting statistics. Overall, among hitters and pitchers, younger brothers played an average of 2.5 years longer than older brothers and in a total of 226 more games.
The roots of the little sibling effect may lie in the way younger siblings strive to match their older siblings on the field. This was the case with Michael Jordan, the youngest of the three Jordan boys and the fourth of the five Jordan children. When the siblings were growing up, Larry — who was born 11 months before Michael — was considered a better basketball player and regularly bested Michael in one-on-one games.
“I don’t think, from a competitive standpoint, I would be here without the confrontations with my brother,” Michael recalled in the ESPN documentary “The Last Dance.” “When you come to blows with someone you absolutely love, that’s igniting every fire within you. And I always felt like I was fighting Larry for my father’s attention. …
“I want that approval. I want that type of confidence. So my determination got even greater to be as good, if not better than, my brother.”
Similar dynamics were at work in the Murray tennis family of Scotland. Elder brother Jamie became a leading doubles player; younger brother Andy has won three Grand Slam singles titles. “I think having an older sibling probably helped Andy to become extra competitive,” said his mother, Judy Murray, in “The Best.” “What helped Andy in particular become that sort of uber-competitor was having an older brother who’s a bit bigger and a bit stronger than him through most of his formative years. And all he ever wanted to do was to beat Jamie.”
As well as honing psychological skills, playing with an older sibling can also accelerate the development of physical skills. The theory is that athletes learn more when they are challenged and fail; the difficulties of these situations can provide feedback that enables athletes to adapt and develop their skills. While older siblings can generally rely on being bigger and stronger to win, younger siblings “playing up” to their older siblings’ level need to develop creativity, decision-making skills and tactical intelligence to keep up — ultimately benefiting them on the field even when they are no longer at a physical disadvantage. Whether consciously or not, older siblings can pass on instructions to their younger siblings. “The ideal strategy for a younger sibling is to try out the same sport in which an older sibling is already established, benefit from a possible teaching effect, and then see if one can do better than the older sibling in that same sport,” Sulloway said.
The amount of informal play that athletes do may also be a predictor of who goes on to become elite. A study comparing soccer players who were offered scholarships from Premier League academies at age 16 with players who were released found that the two groups had accumulated a nearly identical number of hours in practice at their academies. But players offered scholarships had spent more than twice as much time per year on informal soccer play — games with family and friends in local streets and parks — than the players who were released. The NBA has also noted that informal play exposes children to more variables — like different roles and positions, court sizes and numbers of players — which can accelerate skill development, creating “smarter learners” used to adapting.
These findings further help explain the little-sibling effect. Younger siblings are generally able to get more informal play at a younger age than those without older siblings, as they can play with their elder brothers and sisters. Firstborns and only children have to wait for their parents to play with them, or for their parents to arrange play dates; those with elder siblings do not.
Parents also give younger siblings a better chance of becoming elite athletes by treating them differently. Parents are notoriously more indulgent of later-born children, letting them go out more at a younger age — including engaging in unsupervised informal play. Compared with older siblings, younger siblings are around 40 percent more likely to be allowed to play dangerous contact sports, so they have more opportunity of making it to the top in these sports. A certain rebellious streak may also benefit younger siblings on the field: In Major League Baseball, younger brothers are 10.6 times more likely to attempt to steal a base and 3.2 times more likely to steal successfully, Sulloway and Zweigenhaft found. Later-born MLB players are also more likely to get hit by a pitch than than their older brothers, suggesting that they’re less likely to be intimidated and less willing to back down from a confrontation — perhaps because those younger brothers were hit by more pitches growing up playing with their elder brothers.
By the time younger siblings follow older siblings into the talent pathway for a particular sport, parents are “more familiar with how to navigate the sporting system,” said Melissa Hopwood, the co-author of the study of Canadian and Australian athletes. “They knew the good clubs, the good coaches, the commitment required, so they had a more informed, deliberate experience rather than flying blind.”
Athletes can also learn from what worked — and what didn’t — for their older siblings. This has been the case with the remarkable Ingebrigtsen family of runners. Three of the Norwegian brothers have won the gold medal in the 1,500-meter race at the European Championships. Jakob Ingebrigtsen, the youngest of the brothers, is the only one who has also won the gold medal in the European Championships’ 5,000-meters event; in 2018, at age 17, he won gold in both the 1,500- and 5,000-meter races.
“Both Filip and him have learned from my mistakes,” said older brother Henrik after Jakob’s first gold medal in Berlin. “I have made a lot of mistakes!
“But every year, we try to optimize our program and all of [our] training and all of your workouts, and Jakob is starting his training with the perfect programs, more or less.” Now, Jakob is turning into another case study for how younger siblings tend to come out on top in sports.