Democratic presidential candidate John Kerry, who discovered only last year the extent of his Jewish roots, lost two relatives in the Nazi genocide (search) of World War II, officials at Israel's Holocaust archive said Thursday.

A brother of Kerry's grandmother died in the Theresienstadt ghetto (search), and a sister vanished in the Treblinka death camp, archivists at Jerusalem's Yad Vashem (search) Holocaust memorial and museum told The Associated Press.

Word of Kerry's Jewish ancestry first surfaced last year when an Austrian genealogist hired by The Boston Globe found that the Massachusetts senator's paternal grandfather, Frederick A. Kerry, was born under the name Fritz Kohn in 1873 in a village in what is now the Czech Republic.

In the early 1900s, the elder Kerry changed his name and emigrated to the United States, presumably under circumstances similar to many of the region's Jews, who migrated to seek better lives and escape anti-Semitism (search).

The news astonished Kerry, a Catholic. He already knew that his paternal grandmother, Ida Loewe, was born Jewish and converted to Catholicism.

On Sunday, the Austrian genealogist, Felix Gundacker, posted on his institute's Web site that a sister and brother of Ida Loewe were among the 6 million Jews who perished in the Holocaust (search). Gundacker named the two as Jenny and Otto Loewe.

Kerry campaign officials confirmed that the two were a brother and sister of his grandmother.

On Thursday, researchers at Yad Vashem in Jerusalem said they located the two names among nearly 3 million entries in its database of Holocaust victims.

Jenny Loewe was born in 1872 and her brother Otto in 1875, according to the data. Both were taken from their home in Vienna to the Theresienstadt ghetto in Czechoslovakia on Aug. 14, 1942. The ghetto held Jews before they were transported to death camps.

Otto perished there. The last record of Jenny is of her being moved on Sept. 26 of that year to the Treblinka death camp (search), where she vanished.

The Treblinka camp, built in 1942, was an extermination facility, not a labor camp. The Nazis brought 800,000 Jews there with the intention of killing them. Almost all of them perished within hours of their arrival, gassed in chambers filled with exhaust from diesel engines.

Some Jews won reprieve by working in the camp, but only a few dozen people survived Treblinka after a daring revolt. Kerry's relative Jenny Loewe is presumed to have died there.

The camp was shut down and dismantled in 1944 before Russian troops overran the area.