Grace Kingsley does not appear in "Kyle XY", but is mentioned in the final episode.
Family & Relationships
- Cassidy - claims to be son
- Kyle - claimed by Cassidy to be her son also, but under dubious circumstances
The name Grace Kingsley is first mentioned when Kyle is looking at what he and Declan steal from Cassidy's apartment: she is listed as his mother on his birth certificate. Kyle remembers seeing the name just before he burns Adam's journal, where she is noted as attendng a Latnok Board meeting.
At the end of the final episode during their fight, Cassidy tells Kyle "You won't do it." Kyle, holding him up by the throat Jessi-style, says "What makes you so sure." Cassidy says "Grace Kingsley...She's your mother too. I'm your brother." End of story, end of series.
We know that Cassidy would lie to save his life. However, they do share some features. And when Jessi and Amanda are looking at Nate's files on Kyle, Jessi sees something distressing and says "I don't believe it." Could that be a record of the embryo that was Kyle? Who indeed was the mother? We'll never know, by way of more of the series.