The Decalvan Brothers appear to be twins, and both wear overalls. Both have wide faces and flowing black hair. The one with the wider face has sharper teeth. Each brother opens one of their eyes which is large and black around the rim, and closes the other which has a scar over it; which eye they open and close are opposite to one another.
They both wear a brown and yellow pirate tricorn hat with polka dots bandanna underneath it. The hat bears their Jolly Roger: two skulls and a cross-bone, with a wavy design over it. They both wear yellow long gloves with razor-sharp nails at the end on both hands.
The Decalvan Brothers have managed to make themselves an infamous reputation in the New World, and have managed to ally themselves with Whitebeard. After Squard, they were Whitebeard's choice in leading the allies to attack Marineford.
They wear gloves with razor-sharp nails at the end, which are most likely used in battle, similar to Sham and Buchi, the Nyaban Brothers of the Black Cat Pirates, albeit much stronger. In the anime, they were able to fight on par with Vice Admiral Dalmatian to stall him.
In the anime, an additional scene was shown that the Decalvan Brothers fought against Thatch and were beginning to overpower him when Ace joined the fight. The outcome is unknown but it is very likely that the brothers were overpowered by the two commanders because after the battle it was stated that the bounty of Portgas D. Ace was risen again.
In the manga they were always standing together, with one brother partly covering the other one, resembling conjoined twins. In the anime they were always standing further away from each other.
In the anime they were given an additional scene of fighting against Vice Admiral Dalmatian when Whitebeard ordered the allies to backup Luffy; this was not shown in the manga.