Legal Question in Real Estate Law in California

Your brother's marriage has no direct legal consequence for your half interest in the house. It may signal a lessening of his interest in the house, and of course you need to keep an eye on payments on the loan, if there is one, since a default on a loan would mean foreclosure.

His marriage may, however, sooner or later result in his wife acquiring some fractional interest in his half. One way that could happen is by outright gift. More likely, he may use community funds to make his mortgage payments, which would give their marital community a sliver of interest in his portion of ownership. This is called a "pro tanto" interest in family law. Nevertheless, I repeat, non of this affects your half interest, which remains 50.000000%.

Another possible effect is that they may want to move in. You didn't say who is living in the house......but if you and he were sharing possession, he can move her in if he wants.

People who co-own property should have a written agreement respecting their rights and obligations and a plan for unwinding the co-ownership when it no longer suits them. Such an agreement will usually override the standard law of co-ownership of real property, and the standard laws do not always provide the outcome the owners want.

You didn't provide much information, so my answer is kind of general, but at least as to your 50% ownership, perhaps your biggest worry is making sure that your (joint ?) commitments to any lender continue to be met.