Following are the possibilities as your question is vague

Case #1: if the children are Boy(s) and Girl(s) (2/3 + 1/3 = 1) - Two gender 

Case #2: If the children are Boy(s) only = Everything is their  

Case #3: If the children are Girl(s) only = Everything is their 

since I am not a scholar of the subject, therefore, I may be wrong