Sister Mary Casey O’Connor has more than 100 sisters. But only one of them is her twin sister: Casey Gunning, who has Down syndrome.

“I wish everyone had someone like her because she just taught me what it means to love and to not expect anything back,” O’Connor told CNA. “And I mean, that’s ultimately our experience of God … Casey, for me, is an expression of God’s love.”

The sisters were featured speakers at Friday’s Life Fest and the 50th annual March for Life in Washington, D.C.

Each of them advocate for life, even if in different ways: O’Connor is a member of the religious community Sisters of Life, while Gunning serves as a teacher’s assistant and an athlete in the Special Olympics.

Describing her sister’s pro-life witness, O’Connor explained that “it’s not even like a conscious thing, she is constantly choosing just to live life to the full — and she receives the gift of her own life, and that, I think, is the most powerful kind of witness that she gives off.”

For her part, O’Connor joined the Sisters of Life, an order dedicated to promoting the inherent dignity and worth of every human person, in 2015.

The late Cardinal John O’Connor founded the Sisters of Life in New York in 1991. Based in the New York area, the order has sisters in Denver; Philadelphia; Phoenix; Washington, D.C.; and Ontario, Canada. The community of more than 100 Catholic religious women profess four vows: poverty, chastity, and obedience, and “to protect and enhance the sacredness of human life.”

Among other things, the sisters dedicate their lives to serving women vulnerable to abortion, offering life-affirming support to pregnant women in need, hosting retreats, evangelizing, practicing outreach to college students, and helping women who suffer after abortion.

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O’Connor took her last name from the founder of the Sisters of Life. But her middle name, she said, comes from her sister.

“She was so honored that I took her name that she started going by Casey Mary,” she said, adding that “Mary” is Gunning’s confirmation name.

Even their shared age is a celebration, O’Connor revealed. While she clarified that they are 39 years old, Casey, she said, is “so happy to be [turning] 40.”

“She loves getting older because she really loves life,” O’Connor explained, saying that every year they spend six months preparing for their birthday, and, every year, they spend another six months winding down from their previous birthday.

In other words, she said, Casey “loves life.”

The youngest siblings in a family of four children grew up in Littleton, Colorado. The two older siblings were adopted, and the twins came as somewhat of a surprise — they were born after their mother was told that she could not have children. 

They have been inseparable ever since.

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“Just her presence in my life has had one of the biggest effects on just shaping my worldview and my view of life, my view of the faith, my view of the human person,” O’Connor said. 

Casey, she said, helped her gain perspective on life.

“She’s kind of helped ground me in things that are important, and, kind of unintentionally, invited me to let go of things that are not as important, especially eternally,” she said. “And I mean, love literally is oozing out of her.”

Sister Mary Casey O'Connor and Casey Gunning, teacher’s assistant and lifelong athlete in the Special Olympics as babies. Courtesy of Sister Mary Casey O'Connor
Sister Mary Casey O'Connor and Casey Gunning, teacher’s assistant and lifelong athlete in the Special Olympics as babies. Courtesy of Sister Mary Casey O'Connor

“She places no judgment, she always forgives, she always gives the benefit of the doubt,” O’Connor continued. “She always sees the good in the other. And I desperately want that for myself and realize how far I am from that.

“But being in her presence invites me to do it, because she just does it naturally.”

Her sister’s presence also had an impact on her vocation.

“Once I met the Sisters of Life, it kind of all made sense that God had been preparing my heart for so many years, learning how to kind of look at each person for who they were, to see the good in them, to see past what, oftentimes, the world fails to see past,” she said. 

O’Connor shared her approach for instances where she might encounter a pregnant woman expecting a baby prenatally diagnosed with Down syndrome — a woman who might feel scared or tempted to choose abortion. She said she would, first of all, listen.

“Because I think it’s so important just to be a space where someone can express the fears, and the sadness, and the sorrow and the kind of maybe a letdown of expectation — and just receive it and validate it,” she said.

“And then, I couldn’t help but share my own experience of Casey and invite a woman to … trust that God gives us gifts in ways that we don’t always expect or want or would choose for ourselves.”

“On a tangible, concrete, human level, Casey has been the tremendous — the tremendous — blessing of my life, and I just want to invite someone else to step out in faith and trust that God desires to be generous in the unknown,” she said.

If people remember one thing from their speeches on Friday, O’Connor said, she wants it to be that “God doesn’t make mistakes, that he knows what he’s doing.”

“And he has a great desire for us to need him, and he actually wants us to need each other,” she added. “That is what Casey and I — the gift that we have in each other — is that he kind of wrote that into the fabric of our relationship from the very beginning.”