We two are one.

I so depend on Iris to supplement my weaknesses that I consider it a waste of time to pay attention to something to which she is better suited.

After 21 years I need my partner, Iris, to have a complete conversation with someone. Not that I have poor social skills--I'm actually quite chatty. But Iris has half the information about our lives. When exactly did we live in Tempe or Seattle? What was that exit we lived off of again? What was the name of that restaurant? "Wait, Iris knows that; I'll get her to join us."

In honor of Valentine's Day, I want to tell you about finding Ms. Right and making it last a lifetime. My story spans four states and two children and is still going strong. It all starts with the right fit.

Iris and I were fast friends when we met in college and soon realized that on every level we meshed like two puzzle pieces. We overpowered friendship. It was more; it was love.

To borrow a sports: phrase, Iris and I are "in the zone," in sync--we flow together effortlessly. We both thought we were straight when we fell in love, so we started out closeted--fearful of family and society, fearful for our jobs. Slowly, together, we pushed that closet door wide. Seven years into our marriage we were both game to move to Tempe for me to go to graduate school, though we had to look at a map to see where exactly Arizona is. Two years and a diploma later, we knew we wanted children. All it took was reading an article about how Seattle has second-parent adoption, and we were there.

"I think Washington is right above California," I said. "No, I think it's right next to California," Iris said.

Apart from geography, Iris's and my strengths and weaknesses are complementary. In fact, I so depend on Iris to supplement my weaknesses that I consider it a waste of lime to pay attention to something to which she is better suited.

Case in point: math. Despite wonderful private schools and even a master's degree, I still add with my fingers. When we first met, I could not balance my checkbook ("Only $103 off; I'm getting better!"). Iris, on the other hand, wanted to be a math teacher when she was growing up, so her checkbook was "down to the penny" ("I was 3 [cts.] off, but I finally found the mistake"). Needless to say, I was happy to yield all money matters to Iris. On those few occasions when I dine out without her, I am always afraid of guessing what the tip should be. I leave extra, just in case.

It's not just conventional math: I cannot even make soup without Iris. I have been making the same Manischewitz matzo ball soup for 20 years. The directions call for 2 1/2 quarts of water. Because I can never remember if that is eight or 10 cups, I call Iris at work every time to ask. It seems it would not be matzo ball soup without that call.

Iris, on the other hand, cannot deal with anything medical. When we started talking about having children, it did not even have to be said that I would be the one to be pregnant. I was more concerned about Iris making it through my labor and deliveries than about myself. And when our older daughter hurt her arm recently--no blood, no broken bones, only a pinched nerve--Iris almost fainted and had to sit with her head between her legs. Iris does the math; I do the medicine.

We have our life together down to a science, each contributing her best skills. When we assemble a new desk or barbecue grill, she deciphers the directions, I do the actual putting together. And while Iris enjoys looking through cookbooks for new recipes, I'm the one who cooks up what she finds. When we first started living together, we took turns cooking. "I have an idea," I said one night as I poured bottled Italian dressing over Iris's naked, overbaked chicken. "Let me do all the cooking for us." She happily agreed.

Occasionally our oneness is inconvenient. When Iris went to the library by herself to get a book, she realized that she does not own a library card--I do. When she was on a rare business trip, I had to call her hotel room twice to ask how to set the alarm clock. I still did it wrong.

Are we a model couple for same-sex marriage? I don't think so. We're just ourselves. And I think that's what makes it work. When it's the right fit, buckle your seat belts and enjoy the ride.

Eisenbud writes the Family Matters column for Advocate.com.