(ranting)
While I agree little bro seems quite the friend-maker type, saying he is precocious because he can easily interact with a girl is such a japanese thing to say.
A lot of people (especially mangakas apparently) fail to understand that kids have an underdevelopped/incomplete hormonal system, meaning they have little to no desire or sexual consideration. Any concept of gender they would have is merely mimicked from parents or surroundings, without really understanding them...
(anyway, just ranting, maybe I even misunderstood the sentence...)