“He was infact family” He was, but from the female side. So, the other contestant to the throne re-acted the so-call Salique law, pretending that the throne couldn’t go “en-quenouille”, which means by the female.
The Salique law was from a Germanic tradition coming from the Francs salien. Clovis put it in writing. It gave the rules for the succession for the lands, excluding the women, but they could still be heritage others possessions. It didn’t concern the succession of the Throne (which is a title), but, well, the lawyers twisted a little bit the concept.

Edward was the son of Edward II and Isabelle of France, daughter of Phillip II Le Bel (the one who slaughter the Templars) and Jeanne I Queen of Navarre.