To be more accurate, your analogy would have to include birthing the 25 year old for the sole purpose of having a source of organs in the future. The analogy cannot be applied without clarification to in vitro derived embryonic individuals and therefore breaks down if you are trying to refer to unknown embryos passed from the feamle body without or soon after implantation.
No, I would not have to birth the 25 year old for that sole purpose.
Approximately 80% of all zygotes go unimplanted. They are life because they are fertilized zygotes, correct?
Therefore, they are the children of that couple. Is it any different donating the organs of one of your children versus donating the organs of another of your children?