Bit of mixed feelings with this one. Big bro has a point. Iori doesn't have much ambition and is not assertive. With the context that there is a danger out there towards Mio, that is definitely a cause for concern for Mio's safety.
However, just remember that Iori only ever found out about the dangers on that very day. And ultimately, Mio chose to stay with Iori and not her brother. So I think that says a lot about her living condition under him. And even with no talents, skills or hobbies, he still made Mio happy. I think that should count for something.