Gronel was the son of Ragnak. He died at the Battle of Thorntree in The Burning Bridge.
Ragnak, being devastated at the loss of his son then took a Vallasvow against Duncan and his family, vowing to kill them if he ever should encounter them. This meaning that, in The Icebound Land, Evanlyn is unable to reveal her identity as being that of Princess Cassandra.
Gronel is only briefly mentioned in the series.