hey,
I wonder, even if the probability so small is, if someone else get the same private key as me could he/she spend my Bitcoins and viceversa? would we have the same Bitcoin Adress?
Yes of course. Though just like what you said the probability is so small like grains of sand. It is all the matter of luck because ever since the creation of crypto I have never been heard of something like the topic had happened. I do hope I am the lucky one who can guess the same private key with those "lost forever" Bitcoins out there.