Can a bank garnish my wages for a loan in default and then same bank garnish my spouse's loan that he has defaulted on?

If you have accounts with them, then they are not garnishing, they are setting off. You need to move your accounts from that bank. If they are garnishing, it is because they got judgments against both of you. You need to contact the bank's attorney and make payment arrangements or file bankruptcy. Bankruptcy would be a more permanent solution.

You probably need to talk with an attorney knowledgeable in creditor-debtor matters and likely provide copies of all your loan and garnishments records in order for the attorney to provide an adequate answer.

Yes: If you have two loans and you defaulted on both, the creditor has the right to pursue collections as to each outstanding loan. It does not matter that you have the same creditor on two different loans; that creditor - your bank - has the right to attempt to collect from each of you. And in our community property state, each spouse is essentially liable for half of the community debts anyway, so as a practical matter, it does not matter much whose loan it was, yours or your spouse's one. The bank can attempt to collect even from a non-liable spouse.