It would be up to the firm to decide what to do, if anything.
No way for anyone here to know what will happen. Many employers frown upon this scenario, but it happens all the time. Often the usual reaction of the employer is akin to the ostrich with its head in a hole the sand. In other words, the employer pretends no problem exists or refuses to believe it exists.
The problem for most employers with these "office romances" is that when the affair ends as almost invariably happens, someone usually leaves, and has to be replaced. The sexual harassment angle may also exist and thent he employer may have to deal with a lawsuit, which can be costly.
It is more problematic if the two individuals are in a supervisor/subordinate relationship than if the two individuals are merely coworkers of equal standing but report to different supervisors, or managers, etc. or the two individuals are able to influence their compensation, etc. to the detriment of others in the firm.