it is wrong to view the older one as somehow different from the others.
if they were 10 years older and the others were 4 or 5 then perhaps but when there is only 2 years between them it is wrong.
my dad said to me once, that my brother gets special treatment because he is the oldest (2yrs) - he then said my sister gets special treatment because she is the baby of the family (1yr) - obviously!!
however, when i pointed out that this may work if there were 6-7 siblings, but when there are only 3, of similar ages, what you are effectively doing is singling one child out as being less important.
he had a large family and to him this was the way his family was and in his eyes 'that way things are' but he hadn't even considered it from my point of view.
never give special treatment. it breeds contempt and arrogance.