Queen Elizabeth Woodville on the death of her husband Edward IV, not trusting the new Lord Protector, sends her son Richard of Shewsberry to her brother the newly made Admiral of the Fleet, Sir Edward Woodville Lord Scales, to learn about warfare. After fleeing Richard III, he takes his nephew Richard of Shewsberry to his aunt Margaret Dowager Duchess of Burgundy.
They Richard and Edward, quietly lived at the court of burgundy until after Richard III, died and lost to Henry. After, Richards death, Elizabeth Woodville, knowing where her son is at loudly proclaims her son Richard IV. She tries to cancel her daughters wedding, but Henry already claiming the title of King by right of conquest insist. After 1485 Richard of Shrewsberry and his uncle Lord scales live openly in court.
Getting support from his aunt and Burgundy, the Holy Roman Empire, he invaded England 1492. Being the unquestioned son of Edward IV, he achieved some local support and early 1493 took London. Capturing Henry VII and executing him the next day and only sparing Margaret Beaufort because her husband, Thomas Stanley's support; he took his sister, Elizabeth of York, and her four children into custody: Arthur, Margaret, Henry, and Elizabeth. To ease tensions he creates his nephew Arthur Tudor, Duke of York and Earl of Richmond and acknowledges Arthur in right of his mother heir presumptive. He also creates his loyal uncle Edward Woodville, Duke of Exeter.
Now on the Throne he is engaged on the negotiation of his aunt Margaret of Burgundy, to Margaret of Austria, and is married in 1495. This increases his claim to the throne as she is a descendant of the House of Portugal, which were the senior blood Lancastrian claimants, giving his future children a better lancastrian claim to the throne then his Tudor nephews.
This is all I got, how plausible? I'm sure there are many holes, I didn't research much.