obj-c does not support multiple inheritance, regardless of what C++ supports. the two languages has only one thing in common: C, and C is not even an object oriented language.
obj-c supports, however, protocols which are much as interfaces in Java. for those who do not speak Java, interfaces is Java's way of emulating multiple inheritance but without the troubles that multiple inheritance bring. in my opinion, the obj-c way is not as good as Java's though.