NEW YORK— The heirs to a New Hampshire teacher who wrote a poem about a “soft kitty” say TV’s “The Big Bang Theory” is violating their copyrights. Edith Newlin’s daughters sued CBS and other media-related companies Monday over the copyright to a song the lawsuit says has repeatedly been used on the sitcom.

According to the lawsuit, “The Big Bang Theory” used lyrics written by Newlin in the 1930s without buying the rights. The lyrics begin: “Soft kitty, warm kitty.”

“The Big Bang Theory” characters have periodically sung a lullaby involving that phrase.

Messages seeking comment from CBS and other companies being sued were not immediately returned.

— From news service reports