The phrase "There's a reason why two people stay together" implies that there's a deeper purpose or connection that keeps a couple united over time. It acknowledges that relationships aren't arbitrary but are based on shared experiences and qualities.
The quote goes on to say, "They give each other something nobody else can," which emphasizes the exclusivity of the bond. It suggests that within the partnership, each person fulfills a specific need or provides something unique, whether it's emotional support, understanding, companionship, or love.
In essence, this quote celebrates the specialness of individual connections in relationships. It conveys the idea that the reasons for two people staying together go beyond external factors and are rooted in the distinctive ways they enhance each other's lives and meet each other's needs, creating a bond that is truly one-of-a-kind.