The Heart Pirates (ハートの海賊団, Hāto no Kaizokudan) are an infamous and notable rookie pirate crew introduced on Sabaody Archipelago around the time the Straw Hat Pirates and Team Natsu arrived there two years ago. Their potential is further seen with the release of Haki by Rayleigh Silvers, against which nearly every notable crewmate was able to withstand, along with the notable crewmates of the Kid Pirates.
Unlike many other pirates from the North Blue, the Heart Pirates do not use a skull and crossbones, but a smiley instead. The Heart Pirates' has protrusions in six directions, and is in fact pretty similar to that of the Don Quixote Pirates, without the cancel sign over it.
At least five crew members, including Bepo and the newly recruited Bart Jean have been confirmed. Later on, more crewmates were revealed, as seen in Chapter 591. It appears that Bepo, Shachi and Penguin are all proficient in martial arts, in which they all seem stylistically similar. Their captain is also the doctor onboard.
The crew appears to have at least nine members, including Law himself. The most prominent feature of the crew is that they all wear the same boiler-suit apparel, other than Law himself, as well as Bart, a new recruit who changed into a black shirt. A similar clothing design has also been seen being worn by the World Nobles' slaves, with the only notable difference being that the Heart Pirates have their jolly roger on their suits.
It can be presumed that they are a strong crew for them to have made it all the way to Sabaody Archipelago, and have a captain with such a high bounty.
With the addition of the new member, famous pirate captain Jean Bart, the crew may have grown even stronger. All crewmembers were able to withstand a blast of Haki from Rayleigh Silvers, though Shachi stated that he almost passed out, which may indicate he is slightly less powerful.
They also seem to have medical expertise, as their submarine is supplied with what looks like a complete operating theater, and their captain is a medic capable enough to heal Luffy and Jimbei while the former was on the verge of death and the latter was severely wounded.
Given that their captain was a former member of the Seven Warlords of the Sea, it is likely that the crew's reputation and strength have increased as well.