
Yes. In terms of being able to register them with the KC. Half brother to half sister is okay but they do suggest the breeder talks to an experienced fellow-breeder before doing so in case there is a 'nasty' in the common relatives. Provided you know what you are doing, I rather like this form of line-breeding but you also need to know when you need an outcross mating, so you don't get too close.
Good point about running into potential problems with buyers who have read all the horror stories about 'incest' (which of course, it's not) LOL
And also about outcrossing - you get the best and the worst when putting two unrelated lines together - especially if they've perhaps not been put together before! This is the joy of line-breeding which fixes type for one thing.