Cymnea, being of the most powerful family in the Chaos House Barimen, is one of the four children of Cornelius the Great. This made her Oberon’s aunt, just … not necessarily by blood or genetics, depending on what limited understanding we have of relations in a Chaos House. Nevertheless, the marriage was arranged and Cymnea became the first Queen of Amber, and gave Oberon three children, before his eye (and loins) wandered:

• Benedict: first child, with all that brings with it.
• Osric: Named for Oberon’s good friend Osric, Hero of Chanicut
• Finndo: Always trying to keep up with his older brothers.

The marriage was declared to have never happened dissolved “Ab Initio”, removing the boys from being in the line of succession. This was done as a consession to Faiella, Oberon’s next wife.

Cymnea was assassinated during Faiella’s lifetime, and there was no evidence of an investigation, which people took to mean that either Oberon, Faiella, or her family commissioned it.