Workplace romances are bound to happen - particularly in larger organisations. There is nothing wrong with this, but there are some ground rules that everyone should follow to ensure minimal impact on reputations and the business.
First and foremost - DISCLOSURE. If you are in a relationship with someone at work, then you need to disclose this to your leader as soon as possible. You do not need to give them all the juicy details, just let them know so that they can decide what, if any, action needs to be taken to ensure no conflicts of interest can arise.
Make no mistake - everyone in the organisation knows you are seeing each other. It is always best that your boss hears it from you, rather than hearing it via the office gossip grapevine.
Secondly, where there is a power imbalance (ie one party is far more senior than the other, or there is a reporting relationship), it should be avoided altogether. History is littered with the downfalls of otherwise great leaders who fell victim to the errors of judgement that come with having a paramour in the workplace. In the past, it was often the paramour who suffered the downfall, but times have changed and leaders are now (rightly) being held accountable for their poor judgement.
It is never appropriate that you are responsible for the remuneration outcomes for someone with whom you are in a relationship.
Thirdly, and I don't want to get into any moral judgements here, but if you are a married person who commences a relationship at work with someone who is either married or single, then you leave yourself open for questions surrounding your integrity and character. This can be damaging to your long term career. In this scenario, it is always best if one of the parties leaves the employer to work elsewhere (as soon as possible) if the relationship is to be pursued, as it allows for a fresh start for both parties.
Fourthly, leave the public displays of affection outside of the office. The workplace is not a place where people want to witness kissing and cuddling - no matter how besotted you might be.
I once had the experience where 2 of my 3 direct reports were in a relationship, one of them was married and the other was separated. This was not disclosed to me and I had to learn of it from others in the business as everyone knew about it, despite this couple thinking they were clever and hiding it well. I addressed the issue with each of them individually, which resulted in the married person breaking down in tears in my office and assuring me that it was finished and that they were professional and it wouldn't be a problem. However, behaviour in meetings indicated that there were clearly some unresolved issues and that negatively impacted on my leadership team dynamic. For me, trust was also breached, which wouldn't have been the case if this relationship been disclosed to me by them (note that I suspected it was happening for months before I had it confirmed).
Some years ago, I encountered another example of a workplace relationship when a senior manager was in a close working relationship with one of the executive team who was 15 years her senior. She leveraged this relationship around the organisation to ensure she got her way, making her unpopular across the business. Over time, she alienated many of her peers and other executive members, but she felt safe as she considered that she had an influential member of the executive wrapped around her finger. When that executive resigned from the business, she was left out on her own, as she had hitched her star completely to his wagon, and he took his wagon away.
Obviously, this is an example of someone who used their sexuality to progress their career - something I fortunately have only witnessed once in my 30+ year career. The most disappointing thing about this case is that the manager in question was a smart, charismatic and capable individual - she would have progressed based on that alone, but instead, she leveraged her sexuality. This may have provided some short-term career advancement, but her inability to work as a team player and build relationships across the organisation ultimately led to her exit from the business.
We all spend a lot of time at work and it is unsurprising that many relationships start that way - it is certainly preferable to sifting through the Tinder minefield out there! The important thing is to remain professional, disclose the relationship as soon as possible and focus on progressing your career in a way in which you can feel proud.