My brother's replies:

Your brother is in Phil after a long stay..How long? 2003 = 9 years

His Filipino passport expired..While he was in Phils? yup

What passport did he use to enter the Phils.... i used Filipino passport upon entry it was stamped

Is he a dual citizen? no not sure, i dont have the papers alien certificate

Did he show both passports on entry? i showed both but only the filipino got stamped