Do you understand the word "cumulative"? The requirement for the Resident Return Visa (subclass 155) is to spend 2 out of 5 years in Australia on a cumulative basis, NOT an consecutive basis.

In other words, lets say you spend year 1 in Australia, year 2 and 3 in Malaysia, fly back on year 4, and back to Malaysia in the middle of year 5, if you have physically spent 2 years in Australia (around 730 days) in that 5 year block, you will get the RRV.

Further reading: Paragraph 155 of the 2nd Schedule of the Migration Regulations 1994 (http://www.austlii.edu.au/au/legis/cth/consol_reg/mr1994227/sch2.html)

The explanatory statement in the
Migration Amendment Regulations 1999 (No. 6) is also worth a read. (http://www.comlaw.gov.au/Details/F1999B00082/Explanatory%20Statement/Text)

I assume that when you say "my brother helps to sponsor for my PR", you are using the Remaining Relative visa (subclass 115) pathway, as the usual pathways (189 et al) no longer take family into consideration.

Remaining Relative visa (subclass 115) visa holders CANNOT sponsor anyone to migrate to Australia.

Have a look at the "What this visa lets you do" section (under the "Visa Holders" tab) of the Skilled Independent visa (subclass 189) page and compare it with the Remaining Relative visa (subclass 115).