Is this real or just a story?
Charles was foolish. How would he trust friend up to that extent? That is foolishness. We should not handle life with foolishness, bet separately.
Kelvin is now rich. If Charles is not rich, Kelvin may win anything brought up by Charles, except if Charles is rich and able to file a law suit with Kelvin. But even where is the evidence that they added money together to bet.
What happened to Charles can happen to anybody. I think the reason why he trusted kelvin maybe before this incident happened they have been handling money issues together. Sometimes we have this particular friend we can trust like a brother, it is never Charles fault for trusting his friend kelvin.