is my move legal (doing so without spouse's permission)?
No. Either the transfer is entirely void, or your brother and your spouse end up being equal co-owners, depending upon the law of the particular jurisdiction.
Furthermore, by trying to evade community property laws, you will very likely alienate a future divorce judge who will probably rule against you on every single discretionary issue in any future divorce and won't hesitate to assume that you are a criminal bad actor in any credibility dispute.
Custody and alimony are highly discretionary issues in a divorce. The relative value of the property distributed in a divorce is a community property state is not very discretionary, but the decision about which particular things each spouse receives in a property division in a divorce is highly discretionary. The judge also has considerable discretion to determine that a party has not sufficiently established that allegedly separate property is not community property. Child support determinations are mostly non-discretionary, but there is more discretion when there are questions of alleged extraordinary child care expenses and for very high income couples.
If not, is there a way besides having any kind of agreement after
marriage that if I end up divorcing, I don't have to divide up my
property equally with my spouse?
No, there isn't. This is one reason that even billionaires in community property states have to make very large settlements if they divorce and didn't have a prenup.
