New Executive Orders from the Kenyan

[BjornF16]

However, if he were to apply as a foreigner to a US school, and accept aid as a foreigner, his US citizenship could be revoked and then the question of citizenship becomes real.

That is not correct. The US actually recognizes dual citizenship. In your brothers case, nothing would happen to his US citizenship by applying to a private institution of learning.

From the State Dept.:

Potentially Expatriating Acts

Section 349 of the Immigration and Nationality Act (8 U.S.C. 1481), as amended, states that U.S. citizens are subject to loss of citizenship if they perform certain specified acts voluntarily and with the intention to relinquish U.S. citizenship. Briefly stated, these acts include:

obtaining naturalization in a foreign state upon one's own application after the age of 18 (Sec. 349 (a) (1) INA);
taking an oath, affirmation or other formal declaration of allegiance to a foreign state or its political subdivisions after the age of 18 (Sec. 349 (a) (2) INA);
entering or serving in the armed forces of a foreign state engaged in hostilities against the U.S. or serving as a commissioned or non-commissioned officer in the armed forces of a foreign state (Sec. 349 (a) (3) INA);
accepting employment with a foreign government after the age of 18 if (a) one has the nationality of that foreign state or (b) an oath or declaration of allegiance is required in accepting the position (Sec. 349 (a) (4) INA);
formally renouncing U.S. citizenship before a U.S. diplomatic or consular officer outside the United States (sec. 349 (a) (5) INA);
formally renouncing U.S. citizenship within the U.S. (The Department of Homeland Security is responsible for implementing this section of the law) (Sec. 349 (a) (6) INA);
conviction for an act of treason (Sec. 349 (a) (7) INA).

Note that applying to a private institution of learning does not qualify as an "expatriating act".