Tell me how do you argue against the identical twins argument?

We know that zygotes have a small probability to split into two so there generally gives us problem here

1)first of all our "alive" and "different DNA" criteria kind of falls short here (mainly to give moral differentiarion between spearm cells and unfertilised ovum cells) Since most pro lifers I see give this argument to differentiate between reproductive cells and zygotes so it's kind of vague at this point here

2)if we want to win or have weight we must find other criterias to morally differentiate between reproductive cells (I'm referring to sperm cells and unfertilised ovum)

And zygotes since different DNA and Being alive aren't the only criteria

3. kinda optional if u genuinely do have sources where zygotes AT THE FIRST moment of splitting have genetic differences (very small but there still is) then correct me on this term honestly pretty easy if you prove this 3rd point here.

Note:I also know that if we aren't able to differentiate them then there would be wayy to much moral vagueness we would be killing babies who are born comatose but at the same time we would be giving sperm cells and unfertilised ovums the same value as that baby so we clearly need to find a consistent moral line where we give zygotes moral worth but not sperm cells or ovum cells we HAVE TO BRING additional criteria to differentiate between zygotes and sperm or unfertilized ovum cells (Also we are using a purely secular argument here okay?)