SALT LAKE CITY — In the last two years, Nathan Kitchen has revealed to his five children that he is gay, gone through a divorce from his wife and grappled with how to stay in a religion that does not condone his lifestyle.

Now comes the toughest task: telling his children that he could be kicked out of the Church of Jesus Christ of Latter-day Saints if he marries a man, and warning his two youngest, 11 and 15, that they might be barred from serving a mission under new church rules.

“It’s almost like they now have to choose between a gay father and a church that they love,” said Mr. Kitchen, a 47-year-old dentist from Gilbert, Ariz. “This is almost too much to bear.”

The changes to the Mormon handbook — disseminated last week to church leaders around the world — say that being in a same-sex marriage warrants ousting from the religion and that children of gay parents must wait until they are 18 and disavow homosexual relationships to be baptized.