Tasha was born in 2337 on the failed colony world of Turkana IV. Her sister, Ishara, was born five years later. Both of their parents were killed shortly following Ishara's birth, after which they were looked after for a few months by "some people" who later abandoned them, leaving Tasha to care for herself and her sister.
Thomas Riker was a result of a transporter accident in 2361 that created two William Thomas Rikers, genetically indistinguishable from each other, with personality and memories identical up to the point of the duplication. One of the duplicates continued to be known as William Riker. The other chose to use his middle name and went on to join the Maquis resistance.