A pre or post nuptial agreement is a contract entered in to between two parties.  As long as both aprties enter in to the contract freely - with no undue duress and knowing their rights - then they can be held bound to the terms that they agree to.  So here is what you need to make sure of.  You need to make sure that you each seek separate legal help here and have some one explain to you your rights under the law to the division of the marital assets.  You need to make sure that there is a clause in the contract that states that you have both sought separate counsel on this matter and have been advised of your rights and liabilities and agree to this division as written.  Good luck.