No, it can never be a ratio of 10:9 because that would mean let's say I'm 9 and my parents are 10 years of age that would have to mean my parents reproduced me at age of 1 years old which is very highly impossible.
Let say the number is 0.5 Then, sum of this number will be 0.5+0.5=1 Now two is twice of 1. Hence, it proved to be correct. And difference between 5 and 1 is 4 which is less than 12. It also match the question condition.
