As stated in title, brother received an offer from amex with his name and RSVP number on the letter, he gave it to me since he does not need it recently
I followed the instruction and logged into the site w/ required RSVP AND ZIP, however, i did not see brother's name or address appeared there. Does it mean this offer is transferable?

It's the amex gold personal card 50K points with 1K spending within 3 months
btw, we live in the same house

Anybody had experience for this situation before? Your suggestion will be greatly appreciated. thanks in advance