The old man.
But the Ari character is the typical Kibbutz Sabra who joined Hagganah then the IDF and then the succession of parties that are today's Labor. Not necessarily modeled after Rabin but pretty much Rabin.
The "brother", the old "terrorist" is probably Begin- who of course wasn't killed.
Notice that even the book and movie are socialist enough that by the end the Dov character abandons the Irgun for the Hagganah.
Israel was created jointly by the United States and the Soviet Union.