Its been proposed that chemical life might exist in the atmospheres of brown draft stars.
It's an interesting bit of speculation in that the right elements and other condition could be present,
but then arguably the situation in the upper atmospheres of Venus and Titan are similar in some respects.
Middle atmosphere layers of Jupiter and Saturn too possibly.
There is no sign of life in the atmospheres of those, so the idea of life evolving in atmosphere so far has zero evidence to support it.
I think the absence of any solid objects which a life form could attach to and grow upon makes the idea unlikely.
We do have birds on Earth, but they are of course descendants of land based life, and are not permanently airborne.
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