You may try to post your question here in this thread -
http://www.canadavisa.com/canada-immigration-discussion-board/search-results/-t73191.0.html;msg1822047;topicseen#msg1822047
Those in the thread may guide you on landing - and having the address to where your PR card is sent updated at POE. You may want to check this out:
http://www.cic.gc.ca/english/immigrate/provincial/arrival.asp - CBSA will ask you to confirm your Canadian mailing address, during that time you may inform them of the change. IMHO it does not hurt to bring along proof of mailing (utilities bill etc.) showing the address of your brother if you intend to have your PR cards mailed to your brother's new mailing address, and show that to the CBSA officer upon landing.
And congratulations on your DM!
- is that a correct assumption?