I want to agree with your (well written) assessment in its entirety but I don’t. My wife and I felt exactly the same as you and yours did durning the pre-awakening period let’s call it. Where my feelings differ surround two words you used extensively: selfishness and challenging. Your response focused almost entirely around the argument that he should have children because of “the challenge” and to learn selflessness. I’ve never thought the same about our journey. Firstly: owning a business is by far and away many more times difficult than raising a child. Seeing as though I was already a business owner when my daughter was born. It was a dramatic change, yes and challenging at times but definitely not even close to the most challenging life experience (business ownership for us). I know it is all relative but I don’t really think it’s all that challenging.
The best way to explain what he is missing out on is this: True, unbridled love and affection punctuated by periods of challenges. No matter how much you think you love “the love of your life,” you will love your child more. No matter how perfect you think your adult world is without children, it will be unimaginably better with. The fun in raising children is the journey. There is never a dull moment as they are always learning and expressing themselves in new and different ways. For example: my daughter is 19 months old and just learned (at day care) to say “no way” she only knows a few handfuls of words but that combination is hilarious. She never just says “no” anymore. When you you ask her if she wants to go to bed she says “no way” or when you want her to do something she says “no way”. When she is having a tantrum she says “no way” to everything. My wife and I can barely contain our laughter. You feel bad for laughing at her but sometimes it’s unavoidable.
To the OP: If you think your life will be fulfilled without the addition of a child, I advise you to spend some time with a close family members child. You won’t bond to every child but sometimes you’ll find one that really makes you think if you’ve made the right decision. It’s usually the cute little girl who takes a liking to you.
It’s an aweful feeling to make it into your 40's (you’re quite close) and only then have a moment of clarity and regret about your childless life. Children aren’t for everyone, I know but I advise you to dig deep and make sure that decision is right for you. We were all in your shoes with your mindset not more than 4 years ago.