Unless he is trying for the sister that he never had, he is doing it because you are young and available. Obviously not real worldly and jaded or you would not be asking about what is going on.
As far as age goes, you are old enough, depending on the age of consent where you live. National origin doesn't really matter. Religion might, but since he has no plans on marrying you, just screwing you, he might be able to overlook religion issues, if you will.
So, he likes you because you are young and available. Religion and country of citizenship be damned. .