[7] Their father, a physician, and mother, an ex-school teacher, chose to register and raise them as female without subjecting them to genital surgeries, which were generally recommended at the time as corrective procedures for infants with disorders of sexual development.

[14] In May 2017, Meghan Daum reviewed Born Both in The New York Times, saying: "Viloria does us the even greater service (it's more of a gift, really) of showing us what it means to live not just as both a man and a woman but also as a third gender that eventually emerges as the right one.

In 2004, Viloria testified before the San Francisco Human Rights Commission on the need to ban medically unnecessary cosmetic genital surgeries on intersex infants and children.

[22] Between 2010 and 2017 Viloria published numerous essays speaking out against nonconsensual medically unnecessary surgeries in publications including CNN.com, The Advocate, The Huffingtion Post, and the Narrative Inquiry in Bioethics.

Viloria is among a handful of American intersex activists[citation needed] who opposed the use of the term "Disorders of Sex Development" since its introduction.

[23] They also argued that being raised to define oneself as disordered is psychologically harmful to intersex youth: While some doctors and parents are, according to supporters of the term like Chase (co-author of the DSD Guidelines and founder and director of ISNA), more comfortable referring to us as having "disorders" than associating with a label supported by homosexuals and transsexuals, I do not believe adopting a pathologizing label to distance ourselves from these groups is a solution, to say the least....

[27] The action resulted in Viloria being invited to participate in the International Olympic Committee's October 2010 meeting of experts on intersex women in sports, in Lausanne, Switzerland, where they lobbied against adopting regulations which require intersex female athletes to undergo medically unnecessary medical procedures in order to compete as women, and against athletes being referred to as individuals with "disorders of sex development".

[18] As a result of Viloria's advocacy, the IOC and IAAF discontinued its use of "disorders of sex development" to describe the athletes in question, and replaced it with "women with hyperandrogenism".

[28][29] In 2012, Viloria co-authored an article in the American Journal of Bioethics, with intersex Spanish hurdler Maria José Martínez-Patiño, the athlete responsible for overturning the IOC's long-standing mandatory chromosome testing policies, which critiqued the IOC's proposed regulations for women with high levels of naturally occurring testosterone (aka hyperandrogenism).

"[32] On Human Rights Day, 2013, Viloria became the first openly intersex person to speak at the U.N., by invitation, at the event "Sport Comes Out Against Homophobia", along with fellow "out" pioneers, tennis legend Martina Navratilova, and NBA player Jason Collins.

[33][34] In 2014, Viloria advocated against the IOC and IAAF's regulations for women with hyperandrogenism on a panel on the Al Jazeera television show The Stream.

[35] They also wrote about the interphobia and common misunderstandings around naturally occurring testosterone which drive sporting regulations for intersex women, in The Advocate.

Their first action, in December 2011, was contacting former Secretary of State Hillary Clinton to request inclusion of intersex people in human rights protocols and protections.