My parents were never married. They dated, but didn't live together. None of the given categories fit my situation. I'm certainly not the only person with this situation! :) Even an "other" category would more closely match the situation.
Below is a link to an article from the FamilySearch Help Center that will assist you in getting your suggestion to the right group. Click on the link and it will take you there.
How do I give feedback to FamilySearch?
@Dawn Robin Finlinson
The Couple Relationship section has always been the most "neglected" one in Family Tree, when it comes to enhancements, so I wouldn't expect any new ideas (or those that have been suggested over many years) to be introduced in the near future.
With regards your specific issue, you have a choice when it comes to how to place yourself in Family Tree in relation to your parents. Either you can add your name under each of them and keep them out of any couple relationship, or you can put them together as a couple (there doesn't have to be any marriage event, etc. to do this) and add yourself below the pair.
A number of users choose the former method when parents (theirs or their relatives / ancestors) did not live together. Otherwise, some users (especially if they feel they were the product of a loving relationship - albeit, one that did not develop into a lasting one) prefer to position themselves so the family of father, mother and child are all clearly connected.
There is no hard and fast rule here. You can explain the facts about the relationship in the Collaboration or Life Sketch sections, if you wish.
If a person's parents were not in a couple relationship, then you can enter them separately. I illustrated this in a comment here: https://community.familysearch.org/en/discussion/comment/385292#Comment_385292
The parent-child relationship would be the default "biological" for both parents, and there would be no need to choose between relationship event types for the non-existent relationship.