Doubt in Sharing Paypal ID, Account Affiliation.....Help needed....

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I and My brother use Mylot from the same computer. And my brother wish to get the payment via My Paypal ID. But recently I found account affiliation section in preference. My doubt is that Who should Affiliate Whom? Should I Affiliate my brother in my account or should he affiliate me in his account.. Or Both need to do the same thing.... I haven't filled the Shared User details also, Should I need to fill that too??? In that section also Who should affiliate Whom?