Twins Brothers 35 Psychology 29 Mistaken identity 26 Siblings 25 Sisters 21 Brothers and sisters 15 more ... Shipwreck survival 12 History 11 Bobbsey Twins (Fictitious characters) 10 Nature and nurture 10 Shipwreck victims 10 Families 9 Survival 7 Child development 6 Death 6 Infants 6 Research 6 Child psychology 5 Family relationships 5 Hispanic American families 5 Magic 5 Man-woman relationships 5 Multiple birth 5 Schools 5 Criticism and interpretation 4 Exploration 4 Fathers and sons 4 Social aspects 4 Conduct of life 3 less ...