Multiply by 2
69 * 2 = 138kg
It should be around 65 kg.
You are too thin.
Actually, children are very different. Generally speaking, girls are slightly lighter and shorter than boys.
Simple calculation method of standard weight
Male: height (CM)- 105= weight (kg)
Female: height (CM)- 100= weight (kg)
The fluctuation range is 5%
Example: male: height 175CM.
175- 105=70 The standard weight is 70kg.
Female: height 160CM.
160-110 = 50 The standard weight is 50kg.