How are Palestinian refugees different from other refugees in the world ?

Palestinian refugees are special in the sense that they are overseen by the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) rather than the United Nations High Commissioner for Refugees (UNHCR). This is because (UNHCR) did not exist as an organization when the ethnic cleansing of Palestine occurred. This, however, confers no special privileges to Palestinians, and can in fact be detrimental to Palestinian refugees compared to refugees from other contexts.
According to the official United Nations website.

Under international law and the principle of family unity, the children of refugees and their descendants are also considered refugees until a durable solution is found. Both UNRWA and UNHCR recognize descendants as refugees on this basis, a practice that has been widely accepted by the international community, including both donors and refugee hosting countries. Palestine refugees are not distinct from other protracted refugee situations such as those from Afghanistan or Somalia, where there are multiple generations of refugees, considered by UNHCR as refugees and supported as such. Protracted refugee situations are the result of the failure to find political solutions to their underlying political crises.

In other words: Not different from other refugees under international law.
Jerash emergency camp for Palestine Arab refugees (pop. 12,000) : East Jordan Credit: UNRWA by George Nehmeh.
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