Well if life begins at conception (of course we really mean something more than mere "life", a turnip is alive) which of my identical twin granddaughters is not "alive"? The split that results in identical twins occurs a few days, as much as a week, after conception. Any later and you get conjoined twins. Which they are not. They are different sizes though. My speculation is that the split was not even, and the little one got a smaller share, resulting in her being a week or so behind the big one. One truly interesting feature is that one of them, the larger one, had the usual two umbilical arteries, but the little one only had one, just like their older sister had. How that happens with identical genes is a bit of a mystery. Thankfully, both the little twin, and their big sister seem to have no significant complications from the SUA.
It does not follow logically, that if life begins at conception, one of your two identical twin granddaughters is not "alive." Even if the split between the two girls happened days after conception, we know that human life came into being at conception, meaning that human life was transmitted to a new generation.
Each individual girl shares in that new life--- the life that began at conception. Technically, you might want to consider the smaller girl as either a clone-offspring of the larger one, or posit that both individuals were present in the zygote in some undetectable way.
That is a technicality. The point is that Human life "began" perhaps a 1,750,000 years ago with Adam & Eve, or protohominid Lucy and her mate Mr. Australopithecus, or whatever --- and dthereafter, human life is "transmitted" every time another generation is conceived.