Single title romance set in frontier west, twin brothers run a cattle ranch, mail order bride

[Lauren]

I read this book in 2003, but I believe it was an early 1980 romance novel. It was a single title romance novel, greater than 300 pages, set in the American frontier/west.

There are twin brothers who run a cattle (?) ranch. One brother is very standoffish, silent strong type; the other brother is nice and very open. The nice brother decides he wants to marry against his brother's wishes and orders a bride.

She arrives and is from the city (she may be a photographer with pale skin). She marries the nice brother, but there is passion between her and the standoffish twin. Standoffish twin hates her and thinks she'll be a burden, but also feels a passion for her.

The book goes on for several years, she and the nice twin have a good marriage. Something happens and he eventually dies. There's also a sex scene that comes after a rattlesnake bite? She is left alone with the standoffish twin and eventually their passion for each other leads to them having sex in the barn. I can't remember how it ends, but I think he leaves because he does not want to betray his brother even though his brother is dead.