After 6 years of studying Arabic, Arab culture, and Middle East history, and after a year of visa interviews almost exclusively with Arabs, I feel like I've got a pretty good handle on how Arabs identify themselves, at least in the Gulf and in the Levant. There's citizenship, which is the passport or travel documents one carries - of course, some people are dual nationals and have two passports, then there are the Palestinians with no citizenship, only travel documents issued by the Palestinian Authority or more commonly the first country to which their family fled in 1948. Then there's national identity - Palestinians usually identify themselves as that first, followed by any secondary identity. For example, "I'm a Palestinian with a Jordanian/American/British/whatever passport." Jordanians with no Palestinian family members will be very clear about that - "I'm Jordanian Jordanian."
I'm not sure if this double appellation was borrowed from American English, with its plethora of hyphenated origins (Italian-American, African-American, Chinese-American, etc), or if it arose on its own in Arabic, but to say that you're Jordanian Jordanian (or Saudi Saudi, or Egyptian Egyptian, and so on) means that not only do you have that citizenship, but your family originates from the territory now covered by the modern country, with no immediate dilution of another nationality in the past few generations. Amusingly, we at the embassy picked up that phrase and used it in our own way - to mean if someone is an American-born, -bred, and -raised, or if they are American by chance (born there while their parents studied in university, but hasn't been back since), or if they are an immigrant. While there isn't a distinction in the services we provide each category, knowing the citizenship history of each person who comes to us for help allows us to understand their particular needs a little better. The Idaho native ("American American") who converted to Islam and moved to Mecca last year will have different needs than the woman who was born in Urbana-Champaign but hasn't returned since the 1980s ("Saudi American") and now wants to get her first US passport, for example.
Someone who is from a blended family will be very clear about that, but he will almost invariably identify himself with his father's nationality. There's an overlap between culture and citizenship law here: in every Arab country I know of, citizenship is passed exclusively through the father. If a Palestinian man married a Saudi or a Syrian woman, the children of this marriage would have no citizenship and would have to carry the same type of travel documents as their father. Also, a wife can usually gain her husband's citizenship, but not the other way around. For the people we dealt with in Saudi Arabia, there seemed to be two categories of citizenship: Arab nations and Western nations. It would be a problem for a Saudi girl to marry a Syrian, or even a Syrian-Saudi, but no one would blink at her marrying a Saudi-American or a Saudi-British. Those nationalities just don't fit into the equation of regional ethnic hierarchies. (I speak of social preferences here, not about the value of marrying a child into an American family as a way to gain citizenship over time for the non-American family. That's a different case entirely.)
Because I talked mostly to Saudis, I got a good grasp of the social categories inside Saudi Arabia. Saudis whose family originates from the area that modern Saudi Arabia encompasses will tell you what tribe they are from, then that they're Saudi - "I'm an al-Anezi, and I'm Saudi." Usually (though this has gotten somewhat more flexible in recent times) tribal Saudis are expected to marry someone from their own tribe. If they don't, relatives can force the dissolution of the marriage or even decide communally (sort of) to evict them from the tribe. Some tribes are from territories that were divided between nations when borders were drawn after World War I with little regard for social realities on the ground (Winston Churchill, I blame you). Recently, there has been a move to grant dual citizenship to these particular tribes in recognition of their family ties to land that is in another country. So you can have a man from the al-Dossary clan who carries both Bahraini and Saudi passports but who will insist that he's Saudi Saudi - because that's the side of the line the majority of the tribe ended up on.
Now, for one's family to originate from Saudi Arabia, as they view it, you have to look back several centuries: someone whose family immigrated to Arabia 300 years ago, who carries a Saudi passport, and who speaks nothing but Arabic will very likely still have a surname such as al-Bakistani, al-Masri (Arabic for Egyptian), al-Bukhari (city in Central Asia), or al-Hindi (Indian subcontinent). Moreover, they will be expected to marry within that same community of "counterfeit Saudis," as some Saudi children will taunt them. They'll tell you that they're Saudis, but they aren't tribal - and that's a big deal. Rough estimates are that about half of Saudi citizens are tribal. This doesn't mean that they live in tents and herd goats for a living out in the middle of the desert, but it does mean a lot in terms of how these Saudis identify themselves.
Sometimes Saudi men marry women of other Arab nationalities (technically it's illegal for Saudi women to do so). Usually the wife will get a Saudi passport, because it's a lot easier to live in Saudi as a citizen than as a foreign national, and the children will, of course, be Saudis. However, it's usually known if someone's mother isn't a "real" Saudi. It doesn't matter much on a day-to-day basis, especially in recent years, but it still has lots of relevance in certain circles - in the Saudi royal line of succession, for example, some princes have been excluded from ascending to the throne because their mothers were not Saudis (Moroccan or sub-Saharan African, for example). The worst cases, it's whispered, are the princes whose mothers were slaves. That's a pretty harsh insult in a Kingdom where slavery was only outlawed in the 1960s and where so much of your social stature depends on your family.
One is supposed to know who one's paternal forebears are, going back at least seven generations, because names are essentially patronymics: A son of B, son of C, son of D, etc, etc. Tribal names now serve as what we'd call a surname for most people, but within tribes, especially larger ones, there are sub-tribal names delineating specific branches of the family. For a tribal Saudi, both the tribal and sub-tribal name are indispensable parts of his identity. (One interesting effect of this is that when an Arab woman gets married, she does not take her husband's name, as that would completely disrupt the naming system and disguise her social status. Children take their father's genealogy and family name.) In other Arab countries, even if a person isn't tribal, usually at some point in the last three generations a stable surname was picked for the family and is used on official documents. However, in some places (Egypt and the Horn of Africa, notably), stable surnames aren't used at all. Let's say we have an Egyptican guy named Sami, son of Mohammed, son of Ahmed. His legal name is Sami Mohammed Ahmed. When Sami has a child, that son will be named Abdullah Sami Mohammed - looks to us like there's a different last name there, but in reality there is no "last" name, just a series of generational names.
In summary, identity is complicated in this part of the world, much more so than we Americans usually perceive. I can't tell you how many Saudis I've met who were dumbstruck that I don't know where my family lived 100 years ago, or from what part of Europe we originally immigrated.
All of the above was supposed to be a prelude to my understanding of ethnicity and identity in Turkey... but that's a lot of information to digest! I think I'll pause here and return to the issue in a few days. If you're confused, you will definitely understand how I felt when I realized just how differently things work in Turkey. I suspect I will be having a lot of these moments in the next few years!