Janel Tigan
Janel Tigan was an unjoined Trill, the older brother of Ezri Dax and Norvo Tigan, and the son of Yanas Tigan.
By 2375, estrangement from his family, in particular his mother, had driven Janel and his brother into criminal activity and they found themselves associated with the Orion Syndicate. Under the pressure of that association, specifically Thadial Bokar, and the continued deterioration of their family life, Janel and Norvo were complicit in the murder of Morica Bilby, a friend of Miles O'Brien and herself an operative of the Syndicate.
Ezri ultimately uncovered her family's ties to the Syndicate and their role in the crime, helping to bring them to justice despite the pain it brought to the family. (DS9: "Prodigal Daughter")