The Shadow of a Noose — Ralph Compton

THEY LOST THEIR PARENTS...
Young twins Jed and Tim Strange lost their father to an outlaw's bullet, and now their mother has succumbed to a fatal illness. Unable to farm their land due to a lack of funds, the twins set out to find their sister -- who left home to avenge their father's death over a year ago.

...AND THEY MAY LOSE THEIR LIVES
Farm life hasn't prepared the twins for the rough-and-tumble cow towns west of Missouri. And before they even begin their search, they're accused of a murder they didn't commit. Just barely escaping a posse's rope, the twins are on the run -- wounded, hounded by the law, and desperately seeking the true killers....