There will be two empty red velvet chairs at this weekend’s 187th Semiannual General Conference — including the one reserved for Mormonism’s top leader, Thomas S. Monson.

Slowed by advancing age and declining health, the 90-year-old president of the nearly 16 million-member global faith is in declining health and will not attend the twice-yearly gathering of Mormon faithful, the LDS Church said Thursday.

Neither will high-ranking Mormon apostle Robert D. Hales, who is in the hospital.

In May, Monson, seen as a “prophet, seer and revelator” by devout Mormons, stopped going to the office and handed over day-to-day oversight of the Utah-based faith to his two counselors in the governing First Presidency.

Monson was not present for Saturday’s women’s session of the conference, watching the proceedings instead from his apartment.

At April’s conference, the frail president delivered two short sermons, but did not appear at half the sessions. Soon afterward, he was admitted to a hospital for a couple of nights after complaining of fatigue and exhaustion.

Monson has been a general authority in The Church of Jesus Christ of Latter-day Saints for more than half a century. He was ordained an apostle in 1963 at age 36 and has led the church for almost a decade.

For his part, the 85-year-old Hales “was admitted to the hospital several days ago for treatment of pulmonary and other conditions,” church spokesman Eric Hawkins said in a news release. “To permit their continued medical attention to Elder Hales, his doctors have determined that he should not participate in the church’s General Conference this weekend.”

Chris Detrick | The Salt Lake Tribune Robert D. Hales, Quorum of the Twelve Apostles, speaks during the afternoon session of the 184th Semiannual General Conference of The Church of Jesus Christ of Latter-day Saints Sunday April 6, 2014.

An apostle for nearly a quarter-century, Hales is fourth in line for the LDS Church presidency, behind Russell M. Nelson, Dallin H. Oaks and M. Russell Ballard.

But Hales has been ailing for a number of years, delivering many of his conference sermons while seated instead of standing at a podium.

Hales has been a Mormon general authority for more than 40 years, including nearly a decade as the faith’s presiding bishop. In that position, he oversaw the church’s vast real-estate holdings and business operations, and was a prime mover in the renovation of the grand Hotel Utah, now the Joseph Smith Memorial Building in downtown Salt Lake City.

He suffered health scares — a couple of heart attacks — even before becoming an apostle in 1994.

His more recent setbacks began in 2011, when poor health prevented him from attending the spring General Conference.

Six months later, speaking at a morning session during the fall conference from his seat and with an oxygen tube, Hales addressed the problem of pain.

“Why is it that the Son of God and his holy prophets and all the faithful saints have trials and tribulations, even when they are trying to do Heavenly Father’s will?” he asked. “Why is it so hard, especially for them?”

Learning to cope with adversity brings growth and spiritual strength, said Hales, who didn’t return for the afternoon session. “He knows your sacrifices and your sorrows. He hears your prayers. His peace and rest will be yours as you continue to wait upon him in faith.”

At the faith’s conference this past spring, Hales was able to stand to give his remarks.

As Latter-day Saints follow Christ, “there will be no disparity between the kindness we show our enemies and the kindness we bestow on our friends,” the apostle told the crowd watching in the giant Conference Center in Salt Lake City and millions more watching via satellite across the globe or streaming online. “We will be as honest when no one is looking at us as when others are watching. We will be as devoted to God in the public square as we are in our private closet.”

Like the parable of the good Samaritan, true believers “cross the road to minister to whomever is in need, even if they are not within the circle of our friends,” Hales said. “We bless them that curse us. We do good to those who despitefully use us. Is any attribute more godly or Christlike?”

As to his and Monson’s absence at the upcoming conference sessions, Mormon believers are used to it.

Apostle and First Presidency absences have become commonplace, given the age of the all-male leaders and the expectation that they serve for life.

In recent decades, both Spencer W. Kimball, president from 1973 to 1985, and Ezra Taft Benson, who led the church from 1985 to 1994, remained mostly out of sight for some years before they died.

Yet there is no talk of allowing them to retire or to serve as emeritus members of the presiding quorums.

“Emeritus status (granted to lower-level general authorities),” LDS officials have reiterated, “is not a consideration for the First Presidency and Quorum of the Twelve [Apostles].”In the modern era, a Mormon prophet who doesn’t go into decline “is the exception, not the rule,” historian Matthew Bowman told The Salt Lake Tribune after the April conference. “The church has evolved a structural support system where the president of the Quorum of the Twelve or a member of the First Presidency will step up and shoulder the burden.”