1. share money between brothers- делить /распределять деньги между братьями 2. share a house with other dwellers - проживать совместно в доме с другими жильцами (квартирантами) 3. share her opinion -разделять ее мнение 4. share in their sorrow - разделять их горе

As for me, the word SHARE means that a person trusts you and shares it with you. By "it" they mean , for instance, their feelings. Or they share some opinion of theirs with you.