The "crowning moment" of Big Brother 5 in the States will air on Thursday night, it has been confirmed.

In the first five weeks of the series, two contestants - both twins - have been switching in and out of the house, with none of the other contestants realising. That will change in the episode to air tonight, however, when all will be revealed.

"This will be the crowning moment in the five years of Big Brother," said co-producer Arnold Shapiro.

The US version of BB has been doing well in the ratings so far this summer, as has CBS's other major reality show, The Amazing Race.