Meredith describes the beginning of her relationship with Marc, straightforwardly, "There was a spark from the start! We had many things in common... I remember saying... 'You are the male version of me!'"
Meredith was referring to an ancient notion that existed in diverse cultures to explain the idea of romantic attraction, in general. These cultures, the Jewish tradition among them, imagined a primordial being, both male and female, that the Divine separated into two. It is that separation that causes each of us to yearn to connect and become whole.
However, if we listen more closely to Meredith and Marc, they add something that these ancient myths leave out. Marc says, "I felt such a strong connection with this beautiful lady, which I have never felt before with anyone else. I never knew what was missing in my life until I met Meredith." And Meredith adds, "I want to marry Marc as I feel like I have known him forever... I had never understood the meaning of soul mates until I met him."
What Meredith and Marc are saying here echoes the words of Rabbi Shlomo Aviner in an address to his students. He imagines that before coming into this world every couple was this one whole primordial being, which coming into this world was separated into two. They then unconsciously search for that long lost half. When they find each other, each joyously connect to that primordial partner.
Finally, Meredith and Marc introduce one more element beyond Aviner's elaboration. Rejoining one's long lost half has a multiplying effect. You learn from your other half, and that makes you better. In turn, together you equal more than the original whole. As Marc observes, "The love and devotion I see Meredith shows Brynn challenges me," and as Meredith says, "I am a better person for having Marc in my life. He... inspires me to be my best."