Amman, Jordan — THEY are brother and sister - Palestinians . . . on opposite sides of a great divide. ''We try to avoid talking about politics most of the time,'' Samira says. ''I think my brother is wishy-washy, and he thinks I am unrealistic.''
Samira is one of those Palestinians who believe that a negotiated settlement with Israel is impossible.
Her brother, Mazen, disagrees. He believes that the Palestine Liberation Organization must join with those Arab states prepared to negotiate peace with Israel.
''If we can engage the Israelis in negotiations on the (Israeli-occupied) West Bank and Gaza, this should be our first priority,'' he says in his home in a comfortable Amman neighborhood. ''We've got to give all the people involved the sense of security they want, the sense of belonging.''
Educated, articulate, reared in the West, and now making their homes in the Middle East, Samira and Mazen (not their real names) are representative of the deep split in the PLO that was all but formalized at last month's meeting of the Palestinian parliament-in-exile.
Such Palestinians sense that they and the movement that represents them are at a crucial turning point. The PLO's military infrastructure has been crushed by the Israelis. The guerrilla organization's fighters are scattered among the Arab states. There is pressure from without and within to choose a new course.
But what course?
Mazen, a political writer, sees hope in King Hussein of Jordan's call to the Palestinians to form a joint negotiating position in an effort to regain the West Bank and Gaza Strip by political means.
Samira, whose husband is a member of the PLO faction that rebelled against chairman Yasser Arafat, prefers armed struggle against Israel.
''I remember when I was 10, and we were living in New York,'' she explains. ''I asked my mother, 'What am I?' She told me that if anyone asked me, I should say, 'I am an American-born Jordanian.' This is one thing I resent in a way. My parents never instilled in me that 'you belong somewhere and you have a role to play.' My parents never said, 'Go back to Palestine.' And they should have.''
Samira and Mazen's parents, Greek Orthodox Palestinians, had four children. Only one, the oldest son, was born in Palestine. The others were born in New York.
''Our family was in New York when the war broke out in 1948,'' Mazen says. ''My father was a correspondent for an Arab news service in Palestine. He and my mother had lived in Haifa, but all our family was in Nazareth - still is. We were the only ones that left.''
After Israel was declared a state, Samira and Mazen's father took a job with the United Nations.
''I still remember that for a while, on his passport it said 'stateless,' '' Mazen says. Eventually, his father took Jordanian citizenship, which three of his four children took in addition to their American citizenship.
The family lived in Switzerland and New York but returned to Palestine twice, to visit relatives.
Samira describes those visits as traumatic.
''I didn't want to move around, to see the street signs written in Hebrew. My relatives wanted to show us around. They were proud of it,'' she explains incredulously.
''Our home was never very politicized,'' says Mazen, who speaks with far more detachment than his sister. ''We were never heavily indoctrinated, although we always knew we were Palestinians.''
Mazen and Samira both trace the awakening of their identities as Palestinians to the 1967 Arab-Israeli war. Samira was 14 and attending high school in Switzerland. Mazen was studying at Syracuse University.
''The '67 war was a very politicizing experience,'' Mazen says. ''It was a humiliating defeat for the Arabs. To be a Palestinian in the States then was awful, the Arabs were the lowest of the low. The defeat of all the Arab armies was a real eye-opener, and the Palestinians decided to take things into their own hands.
''I became very active, doing speeches, trying to present the Arab position.''
Mazen says he watched the rise of the PLO with some excitement but never joined.
''Terrorism is not a good thing. But everything else had failed. It was the inevitable consequence of a national struggle. We all thought that maybe now the world would stand up and take notice.''
For Samira, the war was excruciating. ''I felt somehow I had the weight of the Arab world on my shoulders. I remember at school, some people were selling oranges from Jaffa to help the Israelis fight the Arabs. One girl came to me and asked me to buy a Jaffa orange - an Israeli orange. I couldn't believe it. I was speechless. I just walked away.''
The PLO for her ''was a very romantic thing,'' Samira says. ''It was a feeling of being part of something.''
The zenith of Mazen's pride in being Palestinian came in 1974, when Mr. Arafat addressed the United Nations as the head of the PLO.
''The whole '73 (Arab-Israeli) war was a matter of great pride for the Arabs. I was in Beirut then, working as a journalist. There was a feeling that maybe now we could make peace. All of a sudden it was OK to be an Arab.''
Samira's return to the Arab world, to Beirut as a college student in 1972, was more troubled.
''I had always wanted to go back, and now I was a foreigner. They teased me about my poor Arabic.''
She threw herself into Palestinian politics, Palestinian social circles, into trying to develop what she calls a political position ''that I could support with logic, not just slogans.'' She never joined the many Palestinian factions that thrived in Beirut's relatively open society.
But she married a leftist Palestinian intellectual who later joined the rebellion that led to Arafat's being driven from northern Lebanon last year. For Samira, Arafat is a symbol who is no longer a revolutionary.
It was in the '73 war, after the Arabs had recouped from 1967 by initially overrunning Israeli positions on the Golan Heights and the Sinai, that Palestinians began to differ openly on which course to take. Samira and Mazen found themselves heading in opposite directions.
Mazen explains: ''It was only after the war that some people talked about the idea of a mini-state on the West Bank and Gaza. I thought it was the best that we could hope for.''
''For me,'' says Samira, ''the idea of a Palestinian state was not a matter of geography. With Israel around I would not be free, I would have no say in the future of my country. They (the Israelis) are a group of people who have an ideology that . . . says they are superior to you.''
Samira maintains that both the existing Arab regimes and Israel would never tolerate a Palestinian state on the West Bank. For her, the only answer is revolution in the Arab world, and the military defeat of Israel, the elimination of a Zionist state. She emphasizes that Jews are welcome to stay in Israel - as long as they are not Zionists.
Her brother dismisses this argument out of hand.
''Samira is a little naive. In theory, what she says is very convincing. But in reality, we've lost. I don't think it is very practical when we talk about the armed struggle. The odds against are formidable. The Americans, the Arabs, the Europeans, and international organizations are all against us.''
In the long run, Mazen sees a confederation among Jordan, a West Bank Palestinian state, and Israel.
''All three are very dynamic people. They could be the Japan of the Middle East if they worked together.''
It is his sister's turn to laugh bitterly. The Israelis, she insists, ''will never make peace. They will never give you anything.''