and後面的句子和前面是並列的，and後面句子的主語是Girls and boys，句子的主幹部分是：（Girls and boys）are not emotionally underveloped. "emotionally"作underveloped（未開發的）的前置定語，意為“在感情上未發育完全”。
consequently意為“因此”，在這裏可以看作連詞；
in their relations with the oppsite sex，意思是在異性關系這壹方面沒有發育完全
所以，這句話後半部分這樣分：
are
consequently
not emotionally underveloped
in their relations with the oppsite sex.