Each of you (mostly, there are the occasional exceptions) have 23 pairs of chromosomes in each cell of your body. For each pair, you got one chromosome from your father and one from your mother. Have you ever considered what that actually means? How many possibilities there are for children from those two parents?
During Meiosis, there’s a stage where segments of chromosomes in a pair can be swapped, but let’s ignore that and just look at whole chromosomes.
For the first of those 23 pairs, doesn’t matter which one we count as first, any will do for this purpose. you could have the first of the pair from your mother (call that 1a) and the first from your father (1a) or the first from your mother (1a) and the second from your father (1b) or the second from your mother (1b) and the first from your father (1a) or the second from your mother (1b) and the second from your father (1b). Four possibilities: 1a1a, 1a1b, 1b1a, and 1b1b.
Now, looking at the second chromosome (again, any will do, just so long as it’s not the first one). For each of those first four, there are again four so: 1a1a2a2a, 1a1a2a2b, 1a1a2b2a, and so on. Sixteen possible children from just the first two chromosomes.
The third, produces four more possibilities for each of that sixteen for a total of 64 possible children. The fourth, four more for each of the 64 or 256. And so on, through 23 pairs of chromosomes.
The number of possible children from a single pair of parents, with 23 pairs of chromosomes each is 70,368,744,177,664.
More. Than. Seventy. Trillion. Possible. People.
Estimates of how many people have ever lived on the Earth, from the first time something recognizeable as Homo Sapiens walked the savannah of Africa to today is about 100 billion. The number of possible people, from a single pair of parents, is about seven hundred times that.
On top of that, official figures claim there are over seven billion people on the Earth today. That’s three and a half billion mother-father pairs, give or take. (Some folk won’t pair at all. Others will pair with more than one other individual.) Seventy trillion possible offspring from each of those three and a half billion pairs? That’s a simply staggering number. That’s nearly two hundred and fifty times as many possible people than all the stars in the visible universe.
And out of all of that, only one of you.