In 1574 Bess arranged a marriage between one of her daughters and the son of the Countess of Lennox. This was a significant match for Bess because the Countess of Lennox was Margaret Douglas, a member of the royal family, being the daughter of Margaret Tudor, Queen Dowager of Scotland and sister of Henry VIII, and therefore, also Queen Elizabeth's first cousin.
In this match, the bride was Bess's daughter, Elizabeth Cavendish, and the groom was Charles Stuart, who was himself also the first cousin of Mary, Queen of Scots, (through their grandmother, the same Margaret Tudor). The groom was also the younger brother of Henry Stuart, Lord Darnley who had been married to Mary until his death. This marriage, therefore, enabled a claim to the throne for any of Bess's grandchildren born of the marriage.
The marriage ceremony took place without the knowledge of Shrewsbury, who, though well aware of the suggested match some time prior to this event, declined to accept any responsibility. Due to the Lennox family's claim to the throne, the marriage was considered potentially treasonable, since Queen Elizabeth's consent had not been obtained.
The Countess of Lennox, mother of the bridegroom, went to the Tower for several months, and Bess was ordered to London to face an official inquiry, but she ignored the summons, and remained in Sheffield until the row died down. The child of the marriage was Arbella Stuart, who had a claim to the thrones of Scotland and England as the second cousin to King James VI of Scotland (later King James I of England), through their great-grandmother, Margaret Tudor.
Arbella was at times invited to Elizabeth's court, but spent most of her time with her grandmother. A BBC documentary[25] showed that Bess very much desired Arbella to become Queen, even imprisoning the young lady to prevent her from eloping. Arbella blamed her grandmother for this, and the two fell out irrevocably when Arbella attempted to run away and marry a man who, as a descendant of Henry VII, also had a claim to the throne. Bess cut Arbella from her will and begged the Queen to take her granddaughter off her hands.
Arbella's royal claim was never recognized. Despite disinheriting Arbella and her eldest son (Henry: for aiding Arbella's escape); Bess later had a "lukewarm reconciliation with her granddaughter.[14] Bess has been an ancestor of the royal line since 1952; Queen Elizabeth II being Bess's descendant through the dukes of Portland, in whose family was Elizabeth II's maternal grandmother, Cecilia Cavendish-Bentinck.