Another Daughter of Time fan here. I've always had my suspicions of Margaret Beaufort or someone supposedly on Richards side with murky motives. Edward V was sickly anyway...
Wrt the point upthread about Philip, Elizabeth and the Romanovs, both were related to both Tsarina Alexandra and Tsar Nicholas, the stand out being Philips blood ties to the Tsarina for DNA testing. Queen Elizabeth was related to the tsarina, the children and her own husband via descent from Queen Victoria. Elizabeth was a direct descendant of Victoria via Victoria's son King Edward VII and Philip via Victoria's daughter Princess Alice. The tsarina and the children were also descendants via Alice.
Philip was an excellent matrilineal match as a great grandson of Princess Alice via an unbroken female line: Queen Victoria of the United Kingdon-> Princess Alice Grand Duchess of Hesse -> Princess Victoria Marchioness of Milford Haven // Princess Louis of Battenberg -> Princess (Alice) Andrew of Greece - > Prince Philip the Duke of Edinburgh. The tsarina had the same descent via an unbroken matrilineal line; she was also a daughter of Princess Alice, Grand Duchess of Hesse and therefore a sister to Princess Victoria of Battenberg. So Queen Victoria-> Alice of Hesse-> Alix (Tsarina Alexandra of Russia) -> Olga, Tatiana, Maria, Anastasia & Alexei Romanov.
Whilat other matrilineal relations were also tested to help ID Tsar Nicholas II, Philip was also related to him via all of his grandparents - just not in a perfect matrilineal line. His maternal grandfather Louis of Battenberg was nephew to wife of Romanov Tsar Alexander II - so distant blood tie there, and on his fathers side, paternal granny Olga Constantinova was the granddaughter of a Romanov Tsar, tieing Philip in that way, and his grandfather King George I of Greece was the brother of a Tsarina; his sister (Philips great auntie) Princess Dagmar of Denmark became Tsarina Maria Feodorovna, mother of Nicholas II. So, King Christian IX of Denmark-> King George I of the Hellenes (Greece) -> Prince Andrew-> Prince Philip. Therefore King Christian of Denmark -> Princess Dagmar (Tsarina Maria Feodorovna) -> Tsar Nicholas II.
Dagmar and George were also siblings of Queen Alexandra of the United Kingdom. So therefore the Queen and Prince Philip- and the Queen and the Tsar and his children, are all related in this way. King Christian IX of Denmark -> Queen Alexandra of the United Kingdom -> King George V of the United Kingdom -> King George VI of the United Kingdom -> Queen Elizabeth II.
The of Kents and the rest of the royals are also related in this way as descendants of George V but if you're wondering where Michael's crazy strong resemblance to the Romanovs comes in, there's an of Russia connection on their maternal side via their mother Princess Marina, as well as further of Greece and Denmark connections via her too.
The Mountbatten connection to Philip is via Princess Victoria.