My fiancé is hesitant to add my name to his house title because he thinks it will cause him to lose the benefits of prop 13 (we are in California). He currently pays very low taxes and wants to keep it this way. Is this true and if so, is there any way around this?

I'm not sure if it will, but its likely it might since a change in ownership could restart the benefits.

I think, once you are married, it will be safe.

Why do you want to get around it? Are you concerned about something happening to him, divorce or what?