please help me

[veeru]

Dear friends, When i was in india my student visa refused on 214(b) grounds. But later my passport expired and i got a new one and with this new passport now, i am in europe on student visa. And now i want to apply for a visitors visa to US for a conference. Should i mention about my previous refusal which is in my old passport. And also my brother is in US with Green card, should i mention that i have a brother there or not.
will these two factors effect my visiting visa application.
Can anyone help me in these two things. Thanks in advance.