Miguel Segura Aguilo’s ancestors were executed as Jews five centuries ago in Spain, but he is not welcome in his local synagogue today.

Gershom Sizomu, who will be ordained this month in Los Angeles as a Conservative rabbi, dreams of setting up the first yeshiva for African Jews in his Abayudayan village in East Uganda.

Rabbi Capers Funnye, spiritual leader of a largely African-American congregation in Chicago, is off to Nigeria to make connections with the Ibo, a community that claims Jewish heritage.

These men, and dozens of other representatives of far-flung communities seeking recognition by the Jewish mainstream, gathered last weekend in San Francisco at an international think tank sponsored by Be’chol Lashon (In Every Tongue), a project of the Institute for Jewish and Community Research.

The Ibo, Lemba and Abayudaya of Africa, the anusim and xuetas of Spain and Latin America, Ethiopian Jews from Israel, Indian Jews from New York and Asian American Jews-by-choice spent three days networking and sharing information about their struggles to join the global Jewish family, a family that is not always eager to embrace them.

“The Jewish community keeps talking about the crisis of intermarriage and the crisis of declining numbers, but meanwhile you’ve got people with Jewish heritage, spiritual seekers, Jewish communities of historical significance, and the Jewish community is doing nothing to help them,” says Gary Tobin, the institute’s president and a long-time advocate of greater openness to those outside the Ashkenazi mainstream.

According to institute research, at least 20 percent of American Jews are racially and ethnically diverse. But old stereotypes about what “real Jews” look like persist, Tobin says.

“Instead of worrying about people being ‘lost’ to intermarriage, why aren’t we extending out ideological borders to include all these people who are so interested in joining us?” he challenges.

Some of these communities have gone through formal conversion, like the 800 Abayudaya of Uganda, who went through a mass conversion in 2002. Others have not, including the Lemba of South Africa, who claim Jewish ancestry and point to the Jewish cultural practices they have maintained for centuries.

Still others languish in a gray zone, notably the anusim of Spain, Portugal and Latin America, known more popularly as the Conversos — those whose ancestors were forcibly converted to Catholicism under the Inquisition, and who now wish to reclaim their Jewish identities. Estimates of their number range from tens of thousands to more than a million.

Some of the anusim claim special status as the descendants of Jews, insisting that they don’t need formal conversion, and a handful of sympathetic rabbis have held “ceremonies of return” for them.

But thousands of others are willing to undergo conversion, says Cuban-born Rabbi Manny Vinas, who runs El Centro de Estudios Judios, a Spanish-language Torah center in New York that tries to guide anusim back to Judaism.

“These people want to return to Jerusalem with their heads held high,” he says, arguing the need for a formal process to help them.

They are thwarted, he charges, by new conversion regulations worked out between Israel’s rabbinate and the Orthodox Rabbinical Council of America, whereby only conversions performed by 15 batei din, or conversion courts, in North America will be accepted in Israel.

That means, he continues, that anyone from Central or South America who wants to convert must travel to North America, a practice that favors the rich.

“For the last 40 years, no conversions in Latin America have been recognized by the chief rabbinate of Israel,” says Vinas. “The only people able to convert are those with enough money to do it in the United States.”

Some of the communities in Be’chol Lashon’s network are far removed from this political struggle. The Lemba of South Africa, who formed their own Lemba Cultural Association in 1948, are still at the stage of finding out who they are, and what Judaism is all about.

Be’chol Lashon is sponsoring a Lemba student in Botswana who is writing his doctoral dissertation on the history of the community. That’s in line with the group’s focus on empowering local leadership, says director Diane Tobin.

The conference “is about building trust,” Tobin says, as well as a way for her group to find out about projects they can support abroad. For example, she notes Be’chol Lashon is funding a medical clinic for the Abayudaya, and has dug wells to bring running water to their five villages.

“We will work with anyone who wants to move forward toward being part of the Jewish community,” she says.