Big Brother 4 (search) is gunning for more friction than usual this summer - adding four "exes" to the house.

The "exes" will be the former spouses, ex-boyfriends or ex-girlfriends (producers would not specify which) of four house contestants who will have entered the Big Bro house a few hours earlier when the show's latest season debuts on Tuesday, July 8.

"We were looking for pre-existing relationships so you start at the very beginning with a story that's already there," co-executive producer Allison Grodner said yesterday.

In the past, the first few episodes of Big Brother typically focussed on how the houseguests - complete strangers - get to know each other. It's later in the season that tempers flare and sparks fly.

"In this case we've got people walking in already with stories, with a past, something that'll start from the get-go," Grodner said.

"These are different kinds of relationships - there are some that were broken off on good terms, some people who want to be reunited and might get back together."

The "exes" were recruited by Big Brother producers after the first nine houseguests were chosen. Both they and their former lovers have no idea that they will be locked away together in the Big Brother house for up to three months.

In addition to the eight "exes," there will be another five singles in the house to add to the confusion, bringing the total number of contestants to 13 - one more than usual.

Like last year, the show will air three times a week. A live edition will air on Wednesdays at 8 p.m. with pre-taped episodes on Fridays and Tuesdays.