If your spouse is having an extramarital affair, generally speaking there are only two things you can do: tolerate it or leave it. Obviously if you choose to tolerate it, then you don't need to worry about it anymore. If you choose to leave it, then you're going to want to express to your spouse what's going on, express to your spouse that this isn't something you are going to tolerate, and that's either going to lead to a separation or a divorce. If it does lead to a separation or a divorce and the court gets involved in analyzing what's going on, as a practical matter the fact of the affair is unimportant. California is a no-fault state, so if somebody cheats on their spouse, that doesn't really have any legal effect. However, if what they are doing is in fact harmful to their children, now it does become relevant and it is something that needs to be looked at. As a general rule though, adults are allowed to do what they want to do and California is not going to make any moral decisions in that regard as long as it doesn't impact anything that is germane to what's happening in the divorce, it's not going to be an issue. However, if you find out that your spouse has been cheating on you can demonstrate that hundreds or thousands or tens of thousands of dollars have been diverted away from your family into this other person: gifts, jewelry, or vacations, or whatever, you can ask the family court to make an order that the community be reimbursed that amount from the person who did that to you.