An Only with a Last is a promising match. Opposites do attract and work, in Birth Order Theory.

Each needs to recognize and be grateful for what the other has to offer. The Only is sensible and conscientious and can help the Last in their shortcomings of being disorganized. In return, the Last can inspire the Only to be more creative and lighten up on their ingrained seriousness.

This does not just happen easily. Last Borns are used to having the more boring details of life being handled by someone else and should make sure they’re not being too dependent on the Only, especially if the Only does not display the typical First Born trait of perfectionism.  (Besides, you don’t want your significant other to feel like they’re parenting you).