That is no excuse. The witnesses are to your signature only and not to the document itself. All they need to be shown is the signature block. They sign to say it's you who signed it. They do not even have to know the nature of the document, and certainly do not have (any right to) to see the contents.
I suspect not, though I could be wrong. The possibility of collusion and common interest arises. The correct procedure is to have independent witnesses who do not stand to gain, even indirectly, from the transaction involved.
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