Only your doctor can tell you what is ideal for you.
The normal weight is 130lbs
depends on your height
The ideal weight is 54 kgs but if you are a bit under or over your still healthy
There is no ideal weight and there is no reason why there is no ideal weight.
You will have to calculate your BMI as it largely depends on height.
AnswerIt depends on the height and bone structure. A 50 inch (4'2") boy will typically weight about 48-52 lbs. 'Ideal weight' is determined more accurately by height and bone structure rather than the age of the individual.
You need to weigh him and measure his height and do a BMI calculation.