And the reactions from the family and those around him were so real and delicately handled, it's hard not to be emotional about them.
First, Kevin (Justin Hartley) candidly implies that William's "gay now," a naive and offensive question that some straight Americans who have never left their protective bubble would ask. Of course, William sets the record straight.
"I'm not gay now," he corrected. "I've always loved both women and men and you know a lot of artists believe sexuality isn't as fixed as it is fluid."
Despite William's insightful response, Kevin taunts Randall about his biological dad being "half gay now." Randall visibly bristles at this offensive characterization.
Luckily, we get to see Randall processing his feelings with his wife Beth (Susan Kelechi Watson). He questions his response and worries about being homophobic.
Beth assures him his uneasiness toward his father's boyfriend is because he doesn't know who Jesse is. She tells Randall he should get to know Jesse the next time he comes by.
Randall tries — and slightly fails — to get to know his father's partner, but his failure spurs a few more special moments about the process of coming to terms with a family member "coming out."
The truth is, bisexuality is still a "taboo" subject for men. As writer Patrick McAleenan of The Telegraph stated:
Many writers and psychologists have wondered whether most self-confessed male bisexuals are simply homosexual men either in denial or trying to 'have it both ways' — having sex with men while holding on to heterosexual privilege. Aside from the potential hurt that may be caused if the bisexuality is revealed, bisexual men face a real threat of abuse or violence.
That threat may be more prominent for Black men: It is incorrectly believed that HIV/AIDS is rampant in the Black community because Black men have unprotected sex with both genders on "the down low."
The fact that "This is Us" shows William fathering a healthy, successful child with a woman while addressing his sexual attraction to men is groundbreaking.
Currently, there are twice as many bisexual female characters on TV than bisexual male characters, according to GLAAD. The few shows that do include bisexual males, like "The Royals" and "Mr. Robot," often link their sexual choices to deceitful personal motives, effectively vilifying their preference and using it as a plot device. Also, these characters are predominately white.
HBO's "Insecure" tackled bisexuality in its premiere season, calling out the Black community for not allowing men to explore their sexuality because they are immediately emasculated. Outside of this, Black male bisexuality is hardly shown on TV.
To show the cast's simultaneous acceptance and "discomfort" with his sexuality brings nuance to a very real situation. And the diverse, realistic responses to William's coming out is a direct sign that "This Is Us" is still damn good TV.