Britain’s Prince Harry and his wife, Meghan, filed a lawsuit in California on Thursday against unnamed paparazzi photographers for allegedly taking “illegal” photographs of their son, Archie.

The lawsuit, filed in the Superior Court of the State of California, County of Los Angeles, cited “serial intrusions” of privacy of the couple’s 14-month-old child, and came as a measure to protect him from the “manufactured feeding frenzy.”

“The Duke and Duchess of Sussex are...