1. Lord Henry Darnley, the handsome poster boy of Scottish nobility, seemed a much better prospect.

結構剖析：這個是一個簡單句。主語是：Lord Henry Darnley，謂語是seemed，表語是：a much better prospect。

在表語中much是副詞，修飾形容詞比較級better。句中的the handsome poster boy of Scottish nobility是做主語Lord Henry Darnley的同位語，說明其長相和身份。

2. It helped that he too had Tudor blood flowing through his veins.

結構剖析：這個句子中的 flowing through his veins是現在分詞短語做后置定語。

3. Too late, Mary discovered she had married a lazy, dissolute drunk, incapable of doing even the minimal things required of a co-sovereign.

結構剖析：這是一個簡單句。主語是：Mary，謂語是discover，he had married a lazy, dissolute drunk, incapable of doing even the minimal things required of a co-sovereign是賓語從句。Too late是狀語，表示時間。

在賓語從句中含有一個形容詞短語incapable of doing even the minimal things required of a co-sovereign后置定語，修飾名詞drunk。此外，還有一個過去分詞短語required of a co-sovereign做后置定語，修飾名詞things。