A man who identified himself as the pair's brother said Saturday that the two had strong family values.
The man repeatedly refused to provide his full name to an Associated Press reporter.
Authorities swarmed the quiet, lakefront condominiums near Fort Lauderdale on Thursday and arrested 30-year-old Sheheryar Alam Qazi and 20-year-old Raees Alam Qazi.
They are charged with plotting to provide material support to terrorists and to use a weapon of mass destruction.
Prosecutors say the two are naturalized U.S. citizens originally from Pakistan.
Federal authorities said the two provided money, property, lodging and communications equipment in a conspiracy to obtain a weapon of mass destruction.