No, your second wife's paycheck may not be garnished; she does not owe back child support for your children. Of course, once her money is in a joint bank account, it could potentially be levied upon (taken for your back child support obligations). Technically, her share of money in a joint account should be exept from levy for your judgments or debts, but in practice, it may be very difficult to prove what portion was hers and what yours, and if the account is levied upon, you'd then be on the defensive, so to speak--having to take action to get her money back.