Sidera Nyx is the younger sister of Vetra Nyx, a member of the Pathfinders' crew aboard the Tempest. She's a communications monitor on the Nexus, although it soon becomes apparent that that's not all she's been up to. She frequently, using her sisters name and contacts attempted to assist with life in Heleus by aiding others, including several exiles. She even released the gene for cats to be produced on the Nexus.
Sid was born on Palaven, her family consisted of Vetra, their father, and mother. Their mother left very early on in their lives and lived on Palaven for the remainder of her life, their father was a military man and also left the young Turians alone pretty early on after not returning from a mission.
However, even though they'd no parents to speak of Vetra and Sid lived on by the only means they could, smuggling. Vetra being Sids' older sister took role as head of the family and took care of Sid as best she could. Sid and Vetra were introduced into the Andromeda Initiative when the superintendent, Kesh, found their small time smuggling operation and instead of turning them in hired them to get her things the Initiative needed to build its projects. After years of running these strange jobs Vetra asked Kesh what they were for only to be shocked by the Initiative, Let's just say a new start was looking pretty good right about then.