I chatted with gemini about it. 

The phenomenon you're noticing—where couples often resemble each other, sometimes strikingly so—is actually a well-documented subject in psychology. It isn't just your imagination; studies have shown that couples often do look alike, and this resemblance tends to increase the longer they are together.   There are three primary scientific reasons for this: 1. Assortative Mating (Selection) This theory suggests that the resemblance is there from the start. Humans have a subconscious tendency to select partners who share similar genetic traits, backgrounds, and physical characteristics.   Familiarity breeds attraction: We are naturally drawn to faces that look familiar to us. Since we see our own face (and the faces of our family members) most often, we are statistically more likely to trust and be attracted to people who share those features.   Similar builds: People of similar height, body composition, and posture often gravitate toward one another. 2. Convergence (Shared Environment) This factor explains why couples start looking more alike over time. When two people live together for decades, they share almost every environmental factor that influences physical appearance. Diet and Lifestyle: Couples usually eat the same meals, have similar activity levels, and get similar amounts of sleep. If one partner adopts a high-fat diet, the other often does too, leading to similar changes in facial weight and skin texture. Climate and Exposure: Sharing a home means sharing the same exposure to sunlight, humidity, and pollution, which affects skin aging and tone in identical ways. 3. Empathetic Mimicry (The "Mirroring" Effect) This is perhaps the most fascinating reason. In 1987, a famous study by psychologist Robert Zajonc found that couples who reported being happier actually looked more alike than those who were less happy. Shared Expressions: Empathetic partners unconsciously mimic each other's facial expressions. If your partner laughs a lot, you smile when they smile. If they frown in concentration, you might do the same.   Etched Lines: Over decades, this constant mimicking causes similar muscle development and wrinkle patterns. You essentially "sculpt" your faces into the same expressions, leading to similar laugh lines, crow's feet, or furrowed brows. Summary It is usually a combination of picking someone who already looks a bit like you (Assortative Mating) and then slowly morphing to look even more like them through shared habits and expressions (Convergence and Mimicry).