WASHINGTON (AP) - President Barack Obama, Vice President Joe Biden and their families plan to attend a prayer service Tuesday morning at the Washington National Cathedral. The 106-year-old Episcopal church has long hosted presidential inaugural services. It was also the site of funerals for former presidents Ronald Reagan and Gerald Ford. The Rev. Martin Luther King Jr. delivered his last sermon there in 1968. Earlier this month, the cathedral said it would begin hosting same-sex weddings that combine civil marriage ceremonies under local law with a blessing from the church. Rev. Adam Hamilton, senior pastor at the United Methodist Church of the Resurrection in Leawood, Kan., will give Tuesday's sermon. Children from the Washington Performing Arts Society's Children of the Gospel Choir will sing.