It matters not whether the cells would produce twins or triplets - it is still an extermination of human life.
You cannot deny that your own life began at the moment of conception.
Let's put those two comments together and look at what non-sense you get to.
So let's start with:
... your own life began at the moment of conceptionSo presumably you mean that the single cell, the zygote, isn't just something that will become me, but actually is me. That is certainly the absolutist (and extremist) view of the RCC.
So let's call this Bob, shall we - the zygote is Bob, rather than at some point in the future will become Bob.
So let's factor in twinning and let's be clear twins are two separate, distinct people, even identical twins - they are two people not one person.
So this zygote is Bob. But what if later on two primitive streaks form and we get identical twins - let's call them Bob and Jim. So when did Jim's life begin - surely the zygote cannot be both Bob and Jim as that is based on something that may or may not happen in the future - i.e. twinning. Otherwise we'd have to ascribe all the identical twinning/triplet etc possibilities to the zygote. So the zygote would have to be Jim, Bob, Stan, Max, Will etc - but if only one embryo develops which is this (and why) and what happened to all the others.
So if Jim's life didn't start at conception, perhaps Jim's life starts when a second primitive streak forms. But why Jim and not Bob. Did both Bob and Jim's lives start at the point of twinning, in which case who was the zygote - was it Eric, and what happened to Eric - did he die to allow Jim and Bob to arise.
And things don't get easier when we consider the rarer phenomenon of embryo fusion in which a single embryo develops from more than one fertilised egg. In this case we have one person derived from more than one zygote. So now we have two zygotes - call them Sarah and Jill - but they fuse and only one person develops - is this Sara, is this Jill and if the former what happened to Jill (did she die) and vice versa. Perhaps the embryo that forms is neither Sara nor Jill, but Erica - in which case what happed to Sara and Jill.
See how your
the zygote is Bob, not just becomes Bob assertion ties you up in knots.
However everything becomes very straightforward when you consider that the zygote is just that, a zygote - it isn't Bob or Jim or Eric nor is it Sara or Jill or Erica. It has the potential to become one, or more of the above or two zygotes have the potential to become one of the above, but the zygote itself isn't any of them yet.