Can you imagine how betrayed you'd feel Kevin, if the mother assured you that it was your child, and you being honourable had agreed to fork out for the child albeit the marriage/relationship had failed. Only to find out that she betrayed you during the relationship, and that she'd screwed around with someone else, before screwing YOU, for the money?
I think I'd be more than a little incandescent with rage.
I totally understand his reaction.
Giok