Sky - is the son of the former King; Erendor and the present Queen; Samara. Sky is now the present king due to the voluntary exit of his father. He also happens to be Bloom's boyfriend and the leader of the Specialists.
Erendor - is the former king of Eraklyon who happens to be one of King Oritel's friend.
Samara - is the present queen of Eraklyon.
The planet Eraklyon has been mentioned often in Season 1. Its first appearance is when Bloom visited there and for the first time, she met Diaspro and confronted her.
Sky invited Bloom and Flora to come over to meet his parents. At the same time, Diaspro was kidnapped and Sky wanted to save him which made Bloom jealous.
Sky invited his friends including the Winx and the specialists to come over to celebrate Eraklyon's 100th anniversary. Sky was also planning to announce something for Bloom, but was suspended when Diaspro tricked Sky to drink the potion which made Sky change his mind to announce for Diaspro instead of Bloom.
The planet Eraklyon has no major roles that could affect the story/plot of the 4th season.
Eraklyon has been mentioned a few times but has no major roles regarding the plot of the season.