Absolutely, Balajee. That is always the issue. When I ask the students to see what their reply would be, it is often ""Sie" for father, "du" for mother, husband addresses wife as "du", wife addresses husband as "Sie" or "du" (depending on the level of emancipation!!!) ..... When I ask why, the answer is always "respect". Automatically the question follows "do you not respect your mother? Do you call her "tum" because you have no respect for her"? The whole problem is a misunderstanding of the concept of "respect".