From the Wikipedia page 
John of Gloucester (c. 1470–1491) was an illegitimate son of Richard III of England. John is so called because his father was Duke of Gloucester at the time of his birth.
The identity of his mother is not known. Katherine Haute, a woman mentioned in household records of the Duke of Gloucester, has been suggested as his mistress and mother of John. Katharine, an illegitimate daughter of Richard III who married William Herbert, 2nd Earl of Pembroke, was probably his sister. They were both half-siblings of Edward of Middleham, Prince of Wales.
He was one of two persons knighted on 8 September 1483 in York during the celebrations which invested his half-brother Edward of Middleham as Prince of Wales.
John is known to have been in Calais by November, 1484 and was officially appointed Captain of Calais by his father on 11 March 1485. His letter of appointment has Richard referring to him as "our dear bastard son". John was not yet an adult and did not exercise the full authority of his position. Robert Brackenbury was entrusted with his safety.
After Richard was killed in the Battle of Bosworth Field (22 August 1485), Henry VII removed John from the position of Captain of Calais position but did not further persecute him and, in 1486, granted him an annual income of 20 pounds sterling. In 1491, an illegitimate son of Richard III is known to have been executed. This was probably John, then in his early twenties, rather than an unknown sibling.
John of Gloucester had no known descendants.