Palpatine's unknown sibling

This individual was one of Palpatine's siblings who escaped the "purge" of his family by his sibling's hand as he/she lived long enough to continue the family line, consumating in the birth of Palpatine's grand-neice Ederlathh Pallopides

Behind the Scenes
It was said that Palpatine killed all of his siblings on the Palpatine family starship in 65 BBY. However, Cosinga Palpatine may have had an affair with another woman, making this unknown person, Palpatine's half-sibling.