Not quite. Benn's story is really quite tragic. He never started with a title at all. In fact, his father, the politician and airman William Wedgwood Benn, wasn't elevated to the peerage (as the 1st Viscount Stansgate) until 1942, when Tony was 17. The eldest son, and thus the one set to inherit the title, was Michael, who was killed when his aircraft crashed as a result of failed instrumentation in 1944. Tony, who was also in the RAF, was devastated by this loss.
Michael had wanted to train to be a priest after the war (their mother was a leading theologian, and Tony is a Christian Socialist), and had no objection to inheriting a title. Tony, on the other hand, fundamentally opposed the aristocratic system, something he was consistent upon his whole life (so far, but I don't expect a deathbed renunciation of his beliefs).
Tony was elected to Parliament in 1950 for a Bristol constituency. He served in this capacity, and campaigning for reform of the peerage, until 1960, when his father's death made him Viscount Stansgate, and suddenly ineligible to sit in the Commons, against his will, and that of the people of Bristol, who re-elected him in 1961 in the full knowledge that he was prevented from taking his seat.
The government recognised, however, that reform was overdue, and, in 1963 passed a law allowing Benn to renounce his unwanted and unsought title, and allowing him to stand. Honourably, the Tory who had taken the Bristol seat when Benn had won the by-election but not been able to enter the Commons, stepped down, and Benn was re-elected.
Sadly, the title still continues, but is in abeyance until Tony dies, when it passes to his eldest son, Stephen Benn, who, of course, as a result of his father's (and others') tenacious fight, has the right to renounce it in turn. I hope he does.