No way Vincent for all his moping and emoness is in fact underneath a very niave little lad who had the hots for a complicated mess of a woman. He blames Hojo for what happened to Lucrecia and over looks the fact that she played a huge part in her own undoing.
If it were his kid he would have stopped them, I have no doubt about that, he had no reason to believe it was and so he had no right to intervene. But he wishes he had done in hindsight because it caused the downfall of his dear Lucrecia