Learn English – “I have been had it” or “I have had it”: which one is correct

"I am" doesn't work because it refers to an action that happens now, where as "Ever since I was a child" refers to a whole period of time, most of which is in the past. "I have been" refers to a continuous action over a period of time that began in the past and continues to the present, so that's what you want to use here.

This is called backshifting. When we use indirect speech, we often put the contents of the speech further in the past.

Let's first take a direct speech sentence:

Lekon Chekon said: "People who were brave enough to fight in WW2 should serve as examples to us".

Now let's report what Lekon Chekon said, and backshift the tenses he used:

Lekon Chekon said that people who had been brave enough to fight in WW2 should serve as examples to us.

This sentence employs indirect speech (no quotation marks). We backshifted were to had been.

Thus, your first sentence is correct. Note that even in the direct speech sentence we can use have been only if Lekon Chekon's words were pronounced during WW2:

In 2015, Lekon Chekon said: "People who have been brave enough to fight in WW2 should serve as examples to us". (WRONG: WW2 ended a long time ago)

In 1942, Lekon Chekon said: "People who have been brave enough to fight in WW2 should serve as examples to us". (RIGHT: WW2 is still going on)