COUPLES GROW TO RESEMBLE EACH OTHER OVER TIME,
because they express empathy through reflecting each other's facial expression; this leads to the formation of similar facial lines.
According to Robert Zajonc (1923 - 2008), exposure influence how a person feels about someone, but it can even change the way a person looks over time. With a group a colleagues, he conducted a study to find out whether the faces of spouses appear more similar after 25 years together. They compared photographs of couples taken during their first year of marriage with those taken 25 years later, and found that couples looked more alike after many years of being together. The researchers decided that empathy was the most likely cause. Time had increased the couple's empathy for each other, and since human emotion is communicated through facial expressions, they may have begun to mimic each others' expressions in the proces of empathizing, resulting in similar wrinkle patterns over time. (Robert Zajonc, Attitudinal Effects of Mere Exposure, 1968)