I know this is from two weeks ago, but just in case I think what you're looking for is:

protected static function boot() {
    parent::boot();
    static::deleting(function($tutorial) { // called BEFORE delete()
        $tutorial->blocks()->delete();
    });
}

If you have children that might need to have their own cascading functions then you might need:

protected static function boot() {
    parent::boot();
    static::deleting(function($tutorial) { // called BEFORE delete()
        foreach($tutorial->blocks as $block)
        {
            $block->delete(); // Causes any child "deleted" events to be called
        }
    });
}

There was a bug/quirk where statements like $tutorial->blocks()->delete(); were not calling the events on each child. I'm not sure if it's been fixed yet, so something like this is safer.