Alex Jones, an online conspiracy theorist who claims the Sandy Hook massacre that killed 20 children and six adults was a hoax, has hired lawyers representing a founder of the neo-Nazi Daily Stormer website to defend him against defamation claims brought in Connecticut by families of seven Sandy Hook victims.

Since days after the 2012 shooting at Sandy Hook Elementary School in Newtown, Conn., Mr. Jones has spread bogus theories that the families were “crisis actors” in a government plot to confiscate Americans’ firearms. The families have endured online abuse, physical confrontations and death threats from Mr. Jones’s devotees.

Marc Randazza and Jay Wolman of the Las Vegas-based Randazza Legal Group are defending Mr. Jones in Connecticut. The lawyers also represent Andrew Anglin, the co-founder of the Daily Stormer, who is being sued for harassment by a Montana woman after Daily Stormer followers subjected her to a torrent of anti-Semitic slurs and threats. Mr. Anglin has cited Mr. Jones as an early influence.

Mr. Jones is also facing lawsuits filed in Texas by the families of two other Sandy Hook victims, but he has different lawyers there. Together, the lawsuits pose a significant legal threat to his InfoWars empire, First Amendment lawyers say.