Why is it obvious? What characterises an "obvious muslim"?
Between being born to a Muslim (regardless if he secular in nature) father would make him Muslim and having a name H-S-N trilateral root should be enough for most folks. Then his school paperworks (Islamic and Catholic schools) both have him down as Muslim. I do not doubt he is a practising Christian, but as far as Islam is concerned, he is a Muslim if not a murtadd.
