Many historians and biographers mention that Catherine Howard was related in some way to Anne Boleyn. Historically, they are joined by a gruesome bond - they were the only two wives executed by King Henry VIII. Catherine married Henry just four years after Anne's execution; yet during those four years, he had married two other women (Jane Seymour and Anne of Cleves.)
Catherine and Anne were first cousins. Catherine's father, Lord Edmund Howard, was the brother of Anne Boleyn's mother, Lady Elizabeth Howard. Edmund and Elizabeth were the children of Thomas Howard, 2nd duke of Norfolk. However, despite their close familial ties, the two women never met. There are many obvious reasons for this - first of all, Anne was about fifteen years older than Catherine. Secondly, the Norfolk family was a tangled collection of cousins (far too many to list here) and, since Catherine was one of many children of a poor younger son, her status was relatively unimportant in the mid-1530s. Third, and perhaps most important, Anne Boleyn disliked her uncle Thomas Howard, the 3rd duke of Norfolk (and formerly earl of Surrey) - he was conniving, opportunistic, and arrogant. This perhaps affected her relationships with all her Norfolk cousins; the only family member she was noticeably close to was her brother, George.
Anne and Norfolk were never close and he only barely managed to hide his dislike while she was queen. When she was arrested and tried, he made haste to distance himself from her at all costs. He also attended her trial and passed judgment against her. His groveling was effective - and still worked four years later when yet another niece (Catherine Howard) was arrested. At Catherine's arrest, virtually every member of the Norfolk family was taken to the Tower - except the duke. His frantic letter to Henry VIII included insults of all his imprisoned relatives, most importantly the 'abominable deeds' of Anne and Catherine. He was certainly an unappealing character but, unlike so many others, he managed to survive in the treacherous Tudor court. Later imprisoned and with his goods seized by the king, Norfolk was condemned to death. Luckily, and ironically, Henry VIII died without signing the warrant for his execution.