Katherine McNamara Opens Up About Future of Mia & William's Sibling Relationship on 'Arrow'

Katherine McNamara was revealed as Oliver Queen and Felicity Smoak’s daughter, Mia Smoak, in the latest episode of strong>Arrow.

But what’s the most puzzling is just how William, played by Ben Lewis in the future, didn’t know he had a sister!

Katherine opened up to press after her reveal and spoke about the relationship between the half siblings.

“It all goes back to the ruin that Star City has fallen into and showing the real lengths that Oliver and Felicity had to go to to keep their children safe,” Kat told ET.

She added to TVLine, “Both [William and Mia] feel extremely abandoned in their own ways, and as much as the two of them are at odds, their relationship is really, really wonderful and so rich, because there are all these different facets to it.”

“First of all, you have this sibling rivalry — ‘you were the biological kid’/'but you were the one who got to experience more of a normal childhood.’ Both of them are jealous of each other, and yet they bond with each other because no one can else can understand the experience of being Oliver and Felicity’s child.”

Katherine continues, “They bond over the struggle that that entails, the feeling of abandonment, and the feeling of being second to the greater good of the city.”

Arrow airs on Mondays on The CW.