She’s succeeded multiple times with Eric, Ridge, and even Thorne.
Over the years, Brooke and Dollar Bill have emerged as a supercouple the fans love.
Why would Brooke betray her sister?

Because Katie asked her sister for a favor.
Suffering from postpartum depression, Katie was convinced that her heart condition had gotten worse and she was dying.
She asked Brooke to help Bill raise their newborn son, Will (perSoap Central).

Brooke did more than that; she fell in love with her sister’s husband.
When Katie returned, now in much better state of mind, Brooke and Bill ended their relationship.
That didn’t last long, however, and soon Katie caught them in bed together and divorced Bill.

Ironically, Bill was in Brooke’s bed because they had just been in a car crash.
Disgusted, Brooke ended things.
Then, she got over things and in 2017, Brooke and Bill finally got married.
Things flamed out quickly when Brooke discovered Bill was the arsonist who burned down Spectra Fashions (perSoaps.com).