If the business rule will not allow you to put non-married males and females in the same companionship (as surmised by Samuel Bradshaw), the screenshots you provided are what I would expect. Once you put the husband and wife together, you cannot add another male (or another female, for that matter) because the system recognizes there is no marriage to any 3rd person. I recommend you provide your special use case as feedback, which will be forwarded to those who set the developer's priorities (though there is no guarantee a code change will occur).