Yes, that was on the forms - you had to include children pictures, even if you are not sponsoring them.
In my case I also didn't include children pictures with the application, but we were not able to get those and we will not going to sponsor them. We wrote a letter explaining the reasons why we can't provide this information, and my husband had to fill in, sign and notarize the special declaration that he understands that if he is admitted as a PR this won't grant a admission to the children.