No, it's not weird. When it comes to relationships, a lot of times girls want something more lasting. They want someone that makes them feel special and like there is no one else as special as they are. So, it's not weird. Guys usually don't feel this way until they are older. As for what age, it depends on the person, really. Some realize it at a younger age than others. Some, it takes until they are in their 50s or 60s. But guys can feel this way when they are 16 or 17. For girls, it can be as young as 14. There's so many things which can decide this, such as having older sisters, or how they grew up, or having been hurt before.