Has there ever been a true rebel in the higher Royal or noble society who charged against a regime or a kingdom that is run by his own family, for altruistic reasons?.
Louis Philippe II the Duke of Orléans, who avidly supported the French Revolution - arguably, the quintessential revolution of the modern era. As First Prince of the Blood, he was one of the most senior members of the ruling Bourbon dynasty. In fact his son would assume the French throne in 1830. I think he qualifies both as a royal and member of the high nobility.
Despite his lofty birth, Louis Philippe believed in the ideals of Jean-Jacques Rousseau, and championed the cause of enlightenment and liberalism. He was a vocal critic of the monarchy in the Assembly of Notables and led a defection of a few nobles to join the Third Estate. He even voted to execute his own cousin, the King of France, in early 1793.
Ironically, Louis Philippe himself was guillotined under the Reign of Terror before the year was out. Given that he sought to abolish the nobility (i.e. by extension, his own privileges) and lost his head when the revolution was "successful", I'd argue he fits the no-personal-gain criterion.
In 1822, Dom Pedro I led a revolution of Brazil against its mother country, Portugal, that was (nominally) headed by his father.
The Glorious Revolution in England, where Mary II (although mostly by her husband William of Orange, later William III) deposed her brother, James II & VII.
I'm not entirely sure if it fulfils your criteria, there was not much more than a skirmish during the actual revolution, but it did result in the Jacobite uprising in Scotland and the Williamite war in Ireland. James being a Catholic meant he had more support in both Scotland and Ireland than his Protestant successors.
Prince Souphanouvong (a minor member of the Laotian royal family) headed the Pathet Lao faction during the Laotian civil war and later became president of the communist republic after the overthrow of the monarchy
Prince Daoud Khan (a minor member of the Afghani royal family) was involved in overthrowing his cousin, King Mohammed Zahir Shah, and rather than declare himself King, proclaimed a republic
Prince (and former, and later, King - its complicated) Norodom Sihanouk was involved in the overthrow of the US-backed Khmer republic by the communist Khmer Rouge and was later Head of State of the communist Democratic Kampuchea during the first year of its existence
protected by Pieter Geerkens Jan 28 '18 at 19:06
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