6. Gemini.
There are two sides to a Gemini. While there is the risk that this sign will be ruled by indecisiveness and occasional bouts of sullenness, the more dominant traits are perfect for maintaining a healthy and loving relationship. Gentle and affectionate, this is a sign that cares deeply about their family and loved ones. Being ruled by Mercury also means that they're willing to communicate, which is an essential trait to a strong marriage.