Two First Borns or two Only children can make a volatile match because they fight over who is best, knows the most, and who is right. Each tries to dominate the other. Both need to be less critical and demanding. They need to get off the perfectionists' bandwagon for this to work and release the other from unrealistic expectations.

The good news is that both have a tendency to be productive and enjoy not having to deal with the other not doing their fair share.  The downside is that First Borns and Only’s are rarely afraid to dish criticism to ones they love, but unironically, they are often more sensitive than most when receiving a curt word or two.  Great care should be taken when criticizing the other because you are both probably good at delivering stings that are especially difficult to heal from.

Note: There are many successful relationships between First Borns and First Borns or Only’s with Only’s. It works when they recognize their likeness and allow for the likenesses and relinquish control over some areas of life they are used to controlling for themselves.  Dividing up chores and their ilk and having faith that the other will succeed are the types of steps couples can make to build trust in the other’s judgment and mitigate anxiety in each other's lives overall.