How does Bruno feel about his sister?

Bruno sees his sister as a hopeless case..... not someone he would choose to play with. Gretel is, of course, older and unlikely to be interested in the same things as Bruno.

'I don't see what else there is to do other than that,' said Bruno sadly. 'I don't even think there's going to be anyone to play with other than Gretel, and what fun is that after all? She's a Hopeless Case.'