Is this considered incest?

Well, considering that it was never flat out stated in "Episode Zero" that they are siblings (weather it was implied or not) it is still left up to the fan base to deside for themselves weather they are brother and sister or not. Also the lack of "word of god" still leaves this open for debate.

I also just noticed the portrait of Murrue Ramius hanging on the wall next to Cathy's head. Taging

deadbreadstick said:

Well, considering that it was never flat out stated in "Episode Zero" that they are siblings (weather it was implied or not) it is still left up to the fan base to deside for themselves weather they are brother and sister or not. Also the lack of "word of god" still leaves this open for debate.

12 years later and yep, turns out episode zero was right and they are brother and sister.