But reckless self-seeking was the main key-note of Warwick's rule. He employed his power unscrupulously to enrich both himself and his family. He took for himself the title of Duke of Northumberland, and ere long allied himself to the royal house by marrying his younger son, Guildford Dudley, to the king's cousin, Lady Jane Grey, the granddaughter of the Princess Mary, the favourite sister of Henry VIII. This alliance led him into schemes which were to prove his ruin. The young king was a bright and precocious boy, showing signs of capacity and strength of will beyond his years. If he had lived, he would have been a man of mark, for already in his sixteenth year he was showing a keen interest in politics and religion, and a tendency to think for himself. But he was incurably delicate, and by 1553 was obviously falling into consumption. [Sidenote: =The succession to the crown.--Will of Henry VIII.=] Dudley saw that his power was bound to vanish on the king's death, if the law of succession was maintained, and the king's eldest sister Mary, the child of Catherine of Aragon, allowed to succeed. The late king had drawn up a will, in which he indicated that, if Edward died, he should be followed first by Mary, and then by her younger sister Elizabeth, the daughter of Anne Boleyn. Henry had then added that, if all his children died heirless, he left the crown to the issue of his favourite sister Mary, the Duchess of Suffolk, and not to the descendants of his elder sister, Margaret of Scotland. [Sidenote: =Edward VI. bequeaths the crown to Lady Jane Grey.=] Now, Lady Jane Grey, the heiress of Mary of Suffolk, was in Northumberland's hands, through her marriage with his son. Accordingly, the duke resolved to persuade the young king to cut his sisters out of the succession, and leave the crown by will to his cousin. The pretext used was that both Mary and Elizabeth were illegitimate, the marriages of Catherine and of Anne to Henry VIII. having both been declared void at different times by the obsequious Parliaments of the last reign. It was, of course, utterly absurd that a boy of sixteen should have the power to make a will transferring the crown, for by English usage the king's title depended on hereditary right and Parliamentary sanction, not on the arbitrary decision of his predecessor. It was entirely unconstitutional to think of disinheriting the two princesses by a mere private document drawn up by their brother. But the young king was persuaded to grant his guardian's request, mainly because he feared the Romanist reaction which he knew would follow on the accession of his elder sister, who had always remained an obstinate adherent of the papacy. [Sidenote: =Execution of Somerset.=]