For those born in Jerusalem, birth certificates shed light on the complexities that have come to define this holiest of cities.

Sami El-Yousef’s grandfather was born in the Christian Quarter of the Old City in 1890; his birth certificate reflected the Turkish Ottoman rule of the time. The British Mandate in Palestine authorized the birth certificate for Mr. El-Yousef’s father, born in the same neighborhood in 1921. The Hashemite Kingdom of Jordan issued Mr. El-Yousef’s birth certificate when he was born in 1960. And when he and his wife Irene had their four children, all born in the Christian Quarter, the state of Israel issued their respective birth certificates.

Regardless of the tremendous changes, instability and violence marking the last century in the Holy Land, the El-Yousef family emphasizes what has remained constant: their Christian identity. Governing authorities may come and go — as have those who make up the Church of Jerusalem that includes modern Israel, Jordan and Palestine — but the “mother church” remains unbroken.

The gravity of history, conveyed in books, buildings and birth certificates, weighs heavily on the Christians of Jerusalem, who maintain an uninterrupted connection with the birthplace of the faith. As they grow, learn, pursue their goals and rear their families in the Holy Land, many contemplate how to live their Christian faith as part of this church.

For Sami El-Yousef, his career has become an expression of this.

For 24 years, he served as finance director at Bethlehem University, which is sponsored by the Holy See. CNEWA then invited him to serve as its regional director for Palestine and Israel. In this capacity, he has interacted with “people in every corner of Palestine and Israel” so as to help this endeavor of the Holy See, known locally as CNEWA-Pontifical Mission, to assess and serve the needs of those most vulnerable.

“It has really been the best seven years of my life,” he says. “All of a sudden, you get that sense of worth, of who you are as a Christian, of your contributions to society and of how critical and important the Christian presence is in a conflict zone.”

This Christian presence is both great and small. Although Christians make up a mere 1.2 percent of the Palestinian population, and 2 percent of the Israeli population, this “minority” — religious and lay — administers some 45 percent of the educational, health care and social service institutions in the region. And even as this Christian population grows more diverse, with Christian migrants from Africa and Asia settling in Israel, religious vocations are in decline, making lay leadership much more common.

“Religious vocations are on the decline generally. So, given the reduction in people entering religious life, we no longer have the leadership of religious to administer the many social service institutions of the church,” says Mr. El-Yousef.

“This is a challenge the Church of Jerusalem has to adapt to as it moves forward,” he says.

“How do we ensure that the charism of these institutions remains strong? What does it mean to be a Christian institution? Does it mean there are merely statutes on campus, a crucifix in every hospital ward, or is it more about the values that govern the institution?”

This challenge, he maintains, is best handled through proper recruitment and formation to ensure that lay leaders and staff fully understand and embrace the charism of the religious congregations that founded these apostolates of service.

Yet emphasizing one’s identity — even, or perhaps especially, in an institutional context — can be a sensational thing in an increasingly polarized setting such as Jerusalem. The city of 880,000 people includes some 370,000 Palestinian Muslims, 500,000 Israeli Jews and a small pocket of about 10,000 Palestinian Christians, 60 percent of whom live inside the Old City. While numerically marginal, this group plays a critical role in times of tension, advocating “for the values of tolerance, coexistence and the respect for human dignity,” Mr. El-Yousef says.

“No matter what happens, you don’t hear Christians calling for revenge. … This places a huge burden on our shoulders, but it’s something many of us understand and accept. Those who find it too burdensome tend to pack up and go, and this is why we’ve seen waves of Christian emigration from here — especially after conflicts.”

The pattern of this emigration, however, has grown more pronounced in recent years. For example, in Bethlehem, the population was 80 percent Christian 80 years ago. Today, Christians make up a mere 18 percent of residents of the town where Jesus was born.

In the face of precipitous population decline, Christians have banded together, attaching less and less importance to the divisions between the Church of Jerusalem’s constituent communities.

“Historically speaking, the various churches that constitute the Church of Jerusalem possess institutions and properties; and each church is still protective about its own interests,” Mr. El-Yousef says.

“On the level of the people, however, you see those divisions less and less. Fifty years ago, it was clear which church you belonged to: Greek Orthodox, Latin Catholic, Syriac Catholic, etc. As Christians continue to emigrate, and as the numbers continue to dwindle, those divisions no longer have the same meaning.

“Now, you’re Christian, period.”