First of all, why are you planning specifically to fly KE from the USA to Brazil? This likely violates fare rules on routings or maximum permitted mileage and hence will be very expensive.

A trusted travel agent (NOT website) might have access to bulk or consolidator fares. There might also be some packages including hotels, etc.

Most of the websites advertising cheap business and first class tickets use stolen or purchased miles. If caught, you could be forced to purchase a full fare ticket. You can also be banned from that airline's FF program.