Bruce, there are huge boundary issues in your marriage:

1. Your wife isn't setting a boundary with your cousin to stop any contact that could be meeting her needs. She by definition is not 'forsaking all others.'

2. Your cousin isn't setting a boundary with your wife to stop contact that is damaging your marriage and your trust.

3. You aren't setting a boundary with your wife to stop getting her needs met by another man.

4. You aren't setting a boundary with your self to stop getting your needs met by another woman.

Marriage isn't an open deal (or at least it shouldn't be.) You must be faithful to each other in every way to have the marriage that will be fulfilling to both of you.

Here is a simple rule to determine what is inappropriate:

There is room in marriage for privacy, but no room in marriage for secrecy. Privacy is what your wife does in the bathroom. You don't need to know about it, but it's not a secret either. Secrecy is when you wife goes into the bathroom to txt another man.

The fact that she is hiding the messages from you is plenty enough reason for the relationship to be inappropriate regardless of what was said.