Sid was born on Palaven, her family consisting of Vetra Nyx, their father and their mother. Their mother left them very early on 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.
With no parents to speak of, Vetra and Sid survived on the only means they could: smuggling. Vetra, being the elder sister, took the 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, Nakmor 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 their contributions to the Andromeda Initiative. After a referral from Kesh, they used the Initiative to create new lives for themselves.
Mass Effect: Andromeda
Sidera is a communications monitor on the Nexus, though it soon becomes apparent that is not all she has been up to. She frequently, using her sister's name and contacts, attempts to assist with life in Heleus by aiding others, including several exiles. She has even released the gene for cats to be produced on the Nexus.
Sometime after Ryder visits Kadara Port, Sid will email Ryder about suspicious findings she's found that implicate some sort of conspiracy against the Nexus. When Ryder goes to speak with her, Sid explains that while monitoring the coms, she noticed that a gang called the Three Sabers have been frequently hitting Nexus outposts and supply vessels with suspicious foreknowledge of Nexus operations. Sid says despite reporting her findings to her superiors, Nexus leadership just mollifies her and doesn't follow through with any investigation. Sid urges Ryder to investigate the Three Sabres and bring the Nexus betrayers to justice. Should Ryder investigate the Three Sabres, it is reavealed that the gang was supplied and hired by Foster Addison to protect Nexus interests but went rogue and started raiding the people they were meant to protect. Ryder and Sid then confront Addison about it and she admits hiring the Outlaws was a mistake but urges they keep quiet about it lest it sparks unrest against Nexus leadership or damage relations with the angara. Sid however believes that the Initiative needs to own up to their mistakes and tell the public. Should Ryder side with Addison, Sid begrudgingly erases the evidence she collected and ceases pursuing the issue out of respect for Ryder. If Ryder sides with Sid, Sid is determined to make sure the truth comes out, resulting in the debacle being broadcasted on the Nexus news service.