Is IBM's OS V7R2 the same as AIX?

It is one of the operating systems supported on IBM Power Systems alongside AIX and Linux as well as on IBM PureSystems alongside AIX, Linux and Windows. source

V7R1,2,3 is a sucessor of OS/400.

A fact on the name;

When IBM announced the new Power Systems line of servers on April 2, 2008, they renamed the operating system from i5/OS to IBM i[3] and changed the version identifier format from VxRxMx (Version, Release, Modification, e.g. V6R1M0) to the more standard format (e.g. 6.1).

AIX and OS/400 are two completely different animals. The only significant relation between the two are that they are both developed by IBM.

AIX is IBM's version of UNIX. OS/400 (i5/Os) is not a Unix operating system. It is the successor to IBM's System 36/38, completely different operating system.

OS/400 does have a Unix based shell that can be used to port and run AIX applications, but that is about it.