The Bible clearly does not prohibit mixed marriages and society’s reluctance to accept such is probably out of prejudice. The Bible teaches us that in Christ there is neither Jew nor Gentile. Racial barriers are removed as far as God is concerned. Culturally and socially racially mixed couples face problems, but if both are believers and are committed to Him and each other, then God will bless their marriage. I would certainly suggest premarital counselling to help them think through all the issues involved.