A sibling rivalry of a different kind produced another win for Great Britain and a heartbreaking defeat for the United States.

Great Britain's Caroline Dubois advanced to the quarterfinals in the lightweight bracket following a split decision over United States' Rashida Ellis. Two judges scored the bout 28-28 even, overruled by three scores of 29-27 in favor of Dubois in their Round of 16 matchup Friday afternoon at Kokugikan Arena in Tokyo.

Both Olympians come from boxing families. The 20-year old Dubois is the younger sister of heavyweight contender Daniel Dubois, while Ellis' older brothers Rashidi and Ronald Ellis are pro boxers.

The opening round saw both boxers initially play to their scouting report before quickly adapting to the other's style. Dubois was sharp, peppering Ellis with jabs and straight lefts out of the southpaw stance. Ellis was able to work her own jab, more so when reversing field in getting Dubois to take the lead which allowed the American to counter with straight right hands. 

The action was as tight in the ring as it was on the cards, with Dubois taking round one on three of the five cards. There was little to separate them in round two as well, with Dubois resuming her counterpuncher role. Ellis grew more comfortable in coming forward, nearly capitalizing on a big moment near the end of the round when Dubois confused the ten-second warning for the bell. Ellis rushed in but was unable to make her pay. 

Still, the fight was on the table heading into the third and final round. Dubois was ahead on two cards with three judges scoring the fight even at 19-19. A crucial point deduction early in round three put Ellis in too far of a hole to pull out the fight.

Referee Sidali Mokretari (Algeria) called for a break when both boxers were tied up on the inside. Ellis hit her twice, with Dubois offering a tap in return. Ellis didn't appreciate the retaliation, tagging her one more time with a slapping right. Dubois sold the flop well enough to have the referee instruct the judges to deduct one point.

Ellis still went on to win the round on the strength of a strong surge down the stretch, though on four of the five rounds. It only pulled her even on two cards, on which she would have won without the point deduction. Dubois was still ahead on two cards, while the one judge who gave her the third round was enough to give her a split decision victory. 

Dubois makes the fifth fighter from Great Britain to reach the quarterfinal round, while also giving her nation an Olympic-leading 13 wins against only three losses. 

Ellis is the fourth American boxer to lose in the past three days. The U.S. team is now 8-5 overall, with the women's team falling to 2-4 and with just 

Jake Donovan is a senior writer for BoxingScene.com. Twitter: @JakeNDaBox