Theories of the origin of life on earth seem to be leaning towards it happening on/in warm damp rocks where RNA like molecules can accumulate in pores. I think there would be problems on Venus - the rocks are too hot, nothing cell like in the atmosphere. But it may be common with a warm damp rock set up which probably was there on Mars.

Organic molecules are fairly common in the solar system on asteroids and the like and probably of non biological origins.

I think the idea with Venus is that life in the atmosphere was a leftover from a more habitable period.