I know this question is two years old (and already answered), but nevertheless…
When I tried this myself, the touches were forwarded, but the buttons no longer behaved like buttons. I also passed the touches along to “super” and now all is well.
So, for beginners that might stumble upon this, this is what the code should look like:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[super touchesBegan:touches withEvent:event];
[self.nextResponder touchesBegan:touches withEvent:event];
}