Josh Hill provided "The 5 worst moments on Friends" at ew.com...
5. The One Where Ross and Monica Kiss | Season 10, Episode 11
If there’s one thing that an objective observer can surmise about the mindset of the Friends writing staff late in the show’s run, it’s that they must have been obsessed with incest. Ross and Monica kissing wasn’t the most aggressive incest storyline, but the fact that it was a throwaway joke that they kissed was pretty lazy, at best.
In the 1970s, studies involving college students revealed that at least 10% of them had already experienced consensual sexual contact with a sibling. It is likely the percentage has increased since, including in the years the characters Ross and Monica would have been living at home and into their early 20s. It would have been entirely realistic if Ross and Monica had a history of experimenting with each other. There are siblings the ages of their characters during the show's run that also experiment and others who are actually in love. Including such scenarios in fiction would be nothing new. Such elements are in the Bible and Greek mythology.
2. The One Where Ross Tries To Bang His Cousin | Season 7, Episode 19I'm not familiar with the plotline, so I infer from this (and nothing else being cited) that Hill's problem is merely the consanguinity of their relationship. That Hill would express such prejudice against this is astounding, given that first cousins can legally marry in about half of US states and only a handful of regressive states criminalize sex between first cousins. Moreover, marriages between first cousins are legal and common in much of the world today, as they have been throughout history.
Ross did some pretty lame things over the course of the show’s run, but this might be the worst. Say what you will about things like thinking he was on a break with Rachel to his temper tantrums later on in the series, but trying to have sexual intercourse with his cousin is too far, even for Ross.
Like other television shows, sitcoms need to touch upon consanguineous sex and consanguinamorous relationships. It is the right thing to do, because these relationships are part of life and yet are unjustly discriminated against. Are there creatives, producers, and executives with the guts to take this on sooner rather than later?
There is much comedy and drama to be mined from this subject, and it can be done in ways that are enlightening and affirming. Viewers need to see that these experiences and relationships can be positive and beautiful, that there's nothing inherently wrong with them, and that they're common enough that they know people who have been in relationships and situations like these. Representation would be the right thing to do for people who are in such relationships.