I'm 38 and live with my twin sister. Our relationship is the most rewarding and challenging experience of my adulthood.

• My twin sister and I live together.
• Our parents didn't encourage competition between us, so we became close friends.

The second time my sister and I were accused of using fake IDs was this year at a Taylor Swift concert. This is strange because we are 38 years old but unsurprising because we are twins. I understand an untrained eye jumping to "fraud" instead of "adult twins" when faced with identical birthdays, addresses, and smiles. If we had fake IDs, we wouldn't have elected to be 38 years old.

Being an adult twin can feel like unpaid labor. We spend an inordinate amount of time fielding invasive questions. We are mixed up at the gynecologist all the time. I was mistakenly put on her car insurance policy. We don't know if we are identical, but we tell everyone we are. It is easier to affirm than to argue the finer points of glasses and bangs not being genetic traits. I find it difficult not to use her as a yardstick by which to measure my successes and failures, which is why my relationship with my twin sister is the most challenging yet rewarding experience of my adulthood.

We've been friends since little

Our parents did not encourage competition, so we easily became friends. In high school, we sat next to each other in alphabetical order, performed in the same choir, and had the same friends. As we got older, our experiences became less the same, and our diverging paths caused me some anxiety. After grad school, she found a dream job to nurture her talents, whereas I have made more than a few pivots and have found less traditional success.

I didn't grow up with my parents asking me why I couldn't be more like my sister — it is strange to hear this question harshly in my own voice.

My relationship with my sister can influence how I feel about myself. The millennial experience of feeling left behind feels exacerbated by the presence of someone with the same experiences and advantages. I had everything she had growing up, why do I feel like a freshly minted adult while my sister has a thriving career and an IRA? Comparison is easy within families but it steals joy when it's your favorite person. The comparison has little to do with the reality of our relationship. Although we are genetically similar, we are individuals on our own journeys with our own goals.

We live together

After graduation, living together was a foregone conclusion but we just never sought to live elsewhere without each other. Research supports that living with family has benefits for mental and physical well-being. Saying that being a twin is having a built-in best friend feels reductive because it removes the agency which allows us to choose each other as friends every day.

My sister provides me with a limitless stream of encouragement that can quiet my comparisons because she loves me because of who I am, not what I do. Our closeness has little to do with genetic similarity or physical proximity.

My sister vibrates at my frequency without hesitation. She's an intellectual sounding board, a treasured companion for life's adventures, and a soothing balm when the world is too raw. Her generosity of spirit is unparalleled. If she weren't my sister, she would still be my best friend.