Short Term Memory Problem

I rounded the corner yesterday morning and found my son Alex attempting to shove the bathroom door open, but Ian-- while in the act of defecating-- was pushing the door the opposite direction, an impressive feat while seated on the commode, and so I asked Alex why he felt the need to get into the bathroom while Ian was engaged in his morning constitutional and Alex said that he needed to brush his teeth and he couldn't wait "because he would forget to do it" and so I told Alex that it is a "rule of the world" that you never interrupt anyone in the act of defecation and the fact that he couldn't remember to brush his teeth in five minutes was his problem, and that he needed to work on his memory and not bother Ian, and Alex told me that he had a hard time remembering to brush his teeth because he had "so much to do, like get dressed and eat breakfast" and I guess that is a lot of things for a seven year old to think about, but I didn't have the heart to tell him that as he grows older, it will just keep getting worse and worse.