We've actually been together for over 2 years, so we have both already encountered each others alters and honestly it hasn't caused any problems. His alters have even met mine. We aren't co-dependant, which is something I personally watch out for because of past experiences. One thing that helps is that we both have a really good handle on how to deal with our disorders. When either of us is feeling triggered we just talk about it. I haven't noticed either of us triggering the other. We rarely even argue. We are both healthy and stable individuals who have the same disorder. This is probably the healthiest relationship I have ever been in. Thanks for the feedback though.