Yes the sign is enforceable. You can probably present your situation to the judge to avoid points.

Generally a BR in and of itself will not be the issue, but the failure to self report may well be.

It is now an issue between your brother and his wife.

It is not clear from these facts you have grounds to sue anyone. If your case is still pending, you need a defense attorney.

Hire a PI.....................................................

When someone asks "can I sue?" the answer is usually yes. But litigation is expensive and time consuming and PayPal can afford very good lawyers.

This is a Q&A forum. You have not asked a question.

As you have not been harmed there is nothing to sue for.

The cost of the lawsuit will far outweigh any potential recovery.

Nothing in your post indicates you have a legal issue at all................