Comfort the child if your words have upset him, or your anger has scared him, and save additional comments for when the child is together enough to listen. Bring up difficult matters during these are the magical times when real change can happen. I have something I need to discuss. Let's take a short walk before your sister arrives. If your child has trouble with the intensity of being corrected, it may be best to bring it up when the child is occupied with an activity.
Some children listen best even when their hands and eyes are busy.
Asking a child to look at you while you reprimand them is not a necessity. Misbehavior occurs at the most inconvenient times. Using timing more wisely is one of the most important tools you have in turning around a relationship.