It’s perfectly legitimate. I know a woman who was very active in ‘bring your daughter to work day’ at my old firm. Actually, I didn’t like her very much, and am not too crazy about the day, but she was criticzed by small minds who found her at fault because she didn’t have a daughter.
Of course, I reminded them that to be fair, she was a daughter.
In any event, I don’t need to be a parent to know the value of a relationship with a parent. Indeed, anyone who finds that amusing just thinks about things too simply. Then again, they probably have to, in order to keep their worldview afloat.