questions - How manyth son to your father?

I know the title sounds stupid, but this is one question that has left me stumped for quite some time. I hope to get an answer in this forum. If the answer is "I am the fourth son of my father", what should be the question?

In general, how do you ask questions with ordinal numbers?

Answer

I don't think you can ask that question directly. The conversation could go something like the following:

How many children does your father have? To which the answer could be three.

You could go on and say:

Which one are you? To which the answer could be I am the youngest, oldest, second, third, etc.

Now the last question might seem ambiguous if it's standing all by its own. But it would make sense once it's in context.