Richard indeed was never asked about the fate of the two princes . Elizabeth Woodville, the boys mother , would not, I believe have let things lie if she had suspected that they were dead. Richard was not,I believe ever accused of this crime during his lifetime ,only later by so called Tudor propogandists.
Richard not marring Elizabeth of York because of her illigitimacy provokes another interesting question. Why did Henry Tudor marry her, or wasn't he so picky ? If in order to marry Elizabeth , Henry had to legitimise her he would have automaticaly made the elder of the two boys Edward V . A possible motive for murder surely ?
It is interesting to note that following the death of Lady Eleanor Butler, with whom Edward IV was said to be pre contracted, he and Elizabeth Woodville could have married again . This would have made their children ligitimate. Did Edward think that the matter would just "go away " Elizabeth Woodville certainly did not know about the pre contract as she was as suprised as anyone on hearing the news.
Henry Tudor married Elizabeth of York, but she was not crowned queen untill 1487, after the birth of their first child, Henry presumably wanting to make sure she could fulfil the Woodville side of the bargain.
Elizabeth Woodville did not even attend her own daughters coronation, and spent the last five years of her life in a convent, having been part of a plot to overthrow her son-in-law Henry Tudor (VII).
Anyone reading this who wishes to know more about this period in history may find the following books usefull
The Daughter of Time by Josphine Tay, a work of fiction but it brought about my interest in the period ,and although published in the 1950's it is still available
Good King Richard ? by Jeremy Potter, this may now be out of print but is worth tracking down at your local library.
and finally Elizabeth Woodville by David Baldwin a good well balanced portrait.