Non-human aliens, like apes? Dolphins? We've already seen non-human intelligences, in our own back yard. Not a great leap to imagine them elsewhere.
We know the probability of the universe evolving intelligent life from scratch is 1. We know nothing about the probability of the universe evolving intelligent life from scratch twice, and the Fermi paradox implies we're very unlikely to ever find out more.
The operative word is 'intelligent'. Probability of life is unknown; but that's not the issue presented.