Many a parent, when inquiring about piano lessons, asks if there is a discount for siblings.  While I understand the parents’ point of view, they apparently haven’t thought this through with the teacher in mind. 

Teaching siblings is usually more work rather than less for the teacher because I have to be careful about possible sibling rivalry.  For instance:  should we or should we not use the same book/pieces for all siblings?  In many cases it is better to NOT use the same book so as to avoid unfair comparisons because I have never had siblings who progressed at the same pace exactly.  One is usually faster than the other, if only for some time, and the resulting comparison can be very frustrating and depressing for the slower student, in particular if it is a younger sibling who happens to be the faster student – which is often the case because they have had the advantage of hearing the older sibling practice and play the pieces they then get to learn!  (They don’t have to be in the same book at the same time for these comparisons to happen.) 

As far as scheduling lessons goes:  while parents may think it would be easier to schedule their children all in a row, for the teacher it is far easier to find time for one 30- or 45-min time slot in a day than for two or more 30-or 45-min time slots in a row, especially in an already fairly full schedule.  

I once heard of a teacher who suggested that we should actually charge more for siblings …