Complex sentence: A younger son, his older brother was Vivian Smith, who the same year left Eton and went up to Cambridge, Vivian Smith was a banker who became Lord Lieutenant of Oxfordshire and in 1938 was created Baron Bicester.
Split into simpler sentences: A younger son, his older brother was Vivian Smith. A banker who became Lord Lieutenant of Oxfordshire and in 1938 was created Baron Bicester.