Yes there is. It is a demonstrable historical fact that he declared his brother’s marriage to Elizabeth Woodeville invalid, his nephews declared bastards and took the throne for himself. Then the princes disappeared. He failed to produce them to quell rumours that they were dead, which was causing a lot of people to turn against him. Suggesting to anyone with common sense that they were almost certainly already dead.
Granted this is not conclusive evidence, but if you apply Occam’s razor to the case, this is certainly the most likely version of events and any other story is frankly, a conspiracy theory...
What happened next - we know, but not why. Evidence was brought to Richard that Edward's marriage to Elizabeth was invalid, and the marriage was declared null and void. We do not know if Richard believed it, or if it was a legal maneuver made in panic because of Elizabeth's failed coup.
What happened to the boys is pure speculation. We simply do not know. We know that Elizabeth Woodville sought sanctuary after her marriage was declared invalid and after the boys disappeared, and that Richard publicly asked her to leave sanctuary and promised her a pension if she did so. She left sanctuary, was not mistreated. Richard kept his word. By contrast, her treatment by Henry VII was much worse!
Richard's actions probably would have been totally different had he been allowed to enter London as a mourner, if Elizabeth had not staged a coup and if Dorset had allowed him to mourn in peace. We know Richard hated London, and loved living in the north.