Complex sentence: Mack's maternal grandfather was Morris Sheppard, U.S. Senator and Representative from Texas, and later his maternal step-grandfather was Tom Connally, the other U.S. Senator from Texas (Sheppard's widow married Connally the year after Sheppard died).
Split into simpler sentences: Mack's maternal grandfather was Morris Sheppard, U.S. Senator and Representative from Texas. His maternal step-grandfather was Tom Connally, the other U.S. Senator from Texas (Sheppard's widow married Connally the year after Sheppard died).