Gerd von Darkmoor is the illegitimate child of Stefan von Darkmoor. He was the result of Stefan raping his mother Rosalyn. During the Serpentwar, Mathilda von Darkmoor was informed of his existence. She saw any illegitimate child a threat to her children's claims, however she welcomed him after both her sons died, and him being the only heir apparent.
From the age of 5, he was raised by Mathilda to be a ruler. Rosalyn was torn from not seeing him, but it was for the best ultimately.