going potty

one day when I was at my daughter's house watching my grandkids; Ei told me she had to go potty. Ei is 2 and in the midst of toilet training, so i was excited to help her learn and get to be the praiser. Ei tried to get her little brother, Bi, to go potty also, but he just walked off. she keep trying to convince him to come with her to the bathroom and sit on the little potty. i told Ei that Bi did not have to go potty and to let him just play. she wanted to know why he did not need to go, and I said "because he is a boy!" Ei turned and looked at him and said "a boooooooy?!" in a long drawn out voice, I then told her that Bi will not be ready to go potty for a long time. Later as I told Ci(my daughter)about the day, and the potty story, she said "Mom! the right answer is because he is still a baby" oh right, and that too.