It appears that life requires a planet of roughly earth size, and similar tempreture levels to earth. Whether that is a 'knife edge' or not depends not on the conditions needed but also on the likelyhood of those conditions.
Are planets of suitable size common in star systems? Is the distribution of planets in our solar system typical of other solar systems? Answer: we don't really know, but current models of planet formation suggest that both answers are 'yes' for main sequence stars.
Note also that life starting and life continuing are different matters.
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