Robert F. Kennedy Jr. faced aggressive questions about his skepticism of vaccines and other issues during the first of two scheduled Senate confirmation hearings.

Mr. Kennedy appears to have most Republicans behind him as he seeks the job of health secretary, though he couldn’t escape his past stances on vaccines and abortion.

Caroline Kennedy, daughter of former President John F. Kennedy, warned senators of her “predator” cousin ahead of his first confirmation hearing on Wednesday. In a letter first reported by The Washington Post, she wrote that his victims included family members and parents of sick children.

If approved, Kennedy will control a $1.7 trillion agency that oversees food and hospital inspections, hundreds of health clinics, vaccine recommendations and health insurance for roughly half the country.

Robert F. Kennedy Jr. was confronted with a number of his baseless claims and a vexing abortion issue. But Republican senators treaded lightly.

Robert F. Kennedy Jr. is seeking the support of the Republican-controlled Senate in his bid to become the nation’s top health official.

Robert F. Kennedy Jr. denied allegations of sexual misconduct toward his former babysitter during his confirmation hearing. He claimed the apology in

Democrats focused on Kennedy's anti-vaccine advocacy. Republicans probed the former Democratic leader on his abortion and agriculture views.

Robert F. Kennedy Jr. arrived at his confirmation hearing to lead the Department of Health and Human Services ready for battle—and wasted no time rallying a demographic that has been among his most loyal soldiers.