Average rent per square meter:1200 ÷120 =10 (yuan),
Personal housing rent payable by Zhang and Wang: 30× 10=300 yuan,
The individual housing rent that Aunt Li's family should bear: 20× 10=200 yuan.
Public area rental fee: 1200-(300×2+200)=400 yuan,
Per capita rent: 400÷(3+3+2)=50 yuan,
Rent payable by Zhang and Wang: 50×3+300=450 yuan,
The rent that Aunt Li's family should bear: 50×2+200=350 yuan;
Answer: It is more reasonable to bear the rent according to the proportion of the shared area of each family, that is, Aunt Zhang's family should bear the rent in 450 yuan; Aunt Wang's family should bear the rent of 450 yuan; Aunt Li's family has to pay the rent, 300 yuan.