Their first child together is Billy Raymond Burton

Helena Bonham Carter and director Tim Burton have once again collaborated to create something unique -- but not another movie.

The Hollywood couple are going to have a second child together, reports People.

"[They] are very happy to be expecting their second child later this year," says the actress' rep, Karon Maskill.

The baby is due in December. The couple already have a 3-year-old son, Billy Raymond Burton, whose godfather is frequent Burton collaborator Johnny Depp. The quirky couple live in adjoining houses connected by a hallway.

Bonham Carter, 41, and Burton, 48, met on the set of his "Planet of the Apes" remake. Since then, she has appeared in all his subsequent films including "Big Fish," "Charlie and the Chocolate Factory," "Corpse Bride" and his upcoming adaptation of "Sweeney Todd: The Demon Barber of Fleet Street," which also co-stars Depp.

The family is currently on vacation in Italy.