Why is it that Owain and Lucina can’t get married

fire-emblem-awakening

So I was playing my Fire Emblem Awakening game recently and I finally got Lucina and Owain to get their S-class relationship (yes this is not my first time playing through the game) and I noticed for the first time that down where it lists the Character's supports (ex: Father, Mother, Child, Wife, Husband) they just have companion. Why can they not become Husband and Wife?

Best Answer

It seems that in NA version of the game they are listed as companions because they are cousins.

Source: http://fireemblem.wikia.com/wiki/Lucina http://www.gamefaqs.com/boards/643003-fire-emblem-awakening/65823321

The strange is that you can do a worse case of incest http://serenesforest.net/forums/index.php?showtopic=38353

Maybe because of the messed timeline. Well.