Samir, who comes from the mixed Druze and Christian area of Mount Lebanon, became active in the Palestinian movement when he was only 13.
It was 1973 and the Middle East was simmering. Just six years earlier, Israel had occupied the West Bank - including East Jerusalem - and the Gaza Strip. By 1975 tensions exploded in Lebanon and civil war broke out.
Samir, a member of the leftist Popular Front for the Liberation of Palestine (PFLP), fought against the first of three Israeli invasions into south Lebanon.
In June 1978 he was arrested in Jordan by local authorities for trying to carry out attacks against Israel.
On 22 April 1979 he crossed over from the coastal city of Tyre in south Lebanon to the Jewish settlement of Naharia along with three other men. The so-called Nasr Operation was aimed at attacking a military base near the settlement in an effort to halt the spread of Jewish settlements.
But the operation was botched and Samir was caught. He was convicted in Israel and sentenced to 542 years in prison for the death of three people in a home he had entered.
Bassam was 17 months old when Samir, then 17, was sent to jail.
Samir al-Qantar in 1979 shortly
before the Nasr Operation
In 1997 Samir earned a bachelor's degree in human science and sociology. But he was only allowed to study after fellow inmates went on a 33-day hunger strike demanding permission to study for a university degree. The authorities relented and allowed study as long as the courses were conducted in Hebrew.
But when Samir wanted to continue his graduate studies with an emphasis on democracy, the prison authorities objected. They said it might damage "the national security of Israel," says Bassam. Samir's proposed thesis was the Contradiction of Democracy and Security in Israel.
Israel and Hizb Allah have been negotiating a prisoner swap for the past three years after the Lebanese resistance group captured three Israeli soldiers from the occupied Shebaa Farms in October 2000. Weeks later, Hizb Allah also seized Elhanan Tannenbaum, who they say is a Mossad spy. Israel insists he is a businessman.
Hizb Allah has been negotiating the release of 24 Lebanese detainees, along with Palestinian and other Arab prisoners held in Israeli jails.
Last November the two sides held talks that Hizb Allah Secretary General Sayyid Hasan Nasr Allah described as "unprecedented". It seemed a breakthrough was near.
But then negotiations faltered when Israel said it would never release Samir. For its part, Hizb Allah said it would never broker a deal without the exchange of all Lebanese detainees and issued a warning it would kidnap more Israelis.
Now Samir's family has finally received a call from Hizb Allah, a call they had been hoping to get for the past 24 years: the bitterest enemies in the Arab-Israeli conflict had reached a prisoner exchange deal and Samir was to be included.
Bassam (R) watches Nasr Allah's
conference with his mother
In the first phase of the two-stage deal, 23 Lebanese, 400 Palestinians and 12 other Arabs would be released this week - on Thursday or Friday - in exchange for Tannenbaum and the three soldiers, widely presumed dead in Israel.
But at a news conference on Sunday, Nasr Allah alluded to the fact that some of the soldiers might be alive.
The bodies of 59 Arab fighters would also be repatriated to Lebanon on Friday.
In the second phase, Samir will be released if Israel receives concrete information on the fate of missing Israeli pilot Ron Arad, whose plane was shot down in Lebanon in 1986 during the war.
Nasr Allah dismissed Israeli allegations that Arad was being held in Iran, saying the airman was not in Tehran or Damascus.
"It was surprising that Sharon went back on his word," said Bassam.
And despite the joy the al-Qantar family is feeling, Bassam is anxious about how his brother, now 41, will adjust.
"Generations have grown and changed," he says.
In 1980 their sister Sana, then 21, died of a stroke. In 1986, their father died. With her oldest son in prison, Samir's mother was forced to provide food, clothing and shelter for her six remaining children - no easy feat with a civil war raging.
Samir's family life will not be the only changes he will face. In the past 25 years, there have been huge leaps in technology, many of which he could not keep up with in jail.
But Bassam knows when he sees his big brother everything will fall into place.