That was pretty much a given ... while a freshman at Occidental College he lived in a dorm that was almost exclusively foreign students. His closest friends at the time were foreign students. Barak Hussein Obama Jr. has been scamming the system most of his life.
We do know the name of someone who lived in Obama's dorm at Occidental and went on to Columbia with him -- Phil Boerner, not a foreigner. We also know the name of his freshman roommate at Occidental -- Paul Carpenter, also not a foreigner. Kenneth Sulzer -- not a foreigner -- lived across the hall.
It's certainly true that many or most of his friends were foreigners -- Imad Husain, Mohammed Hasan Chandoo, Wahid Hamid, and later Vinai Thummalapally and Sohale Siddiqi. David Remnick says Obama's floor in Haines Hall was "unusually diverse" for Occidental at the time, but so far evidence hasn't turned up that it was "almost exclusively foreign students."
Given that Obama gravitated to non-White classmates (yet apparently not to African-Americans) he didn't have to be in an all or mostly foreign dorm to end up with mostly foreign acquaintances.
Barak Hussein Obama Jr. has been scamming the system most of his life.
No legitimate and legal reason to have multiple social security numbers.