There are many factors that can influence BMR, such as age, gender, body composition, and physical activity level. It is possible that despite leading independent lives and engaging in different activities, you and your twin sister have similar body compositions and physical attributes that result in the same BMR. It is also possible that you both have similar genetic predispositions that contribute to your BMR being the same. Ultimately, the reason for having the same BMR could be a combination of genetics and lifestyle factors.
