Our sprogs are 46 and 48 years old. They are still infants as far as we are concerned. Parents are like that.

Loving and or caring about someone has nothing to do with religion.

Pure biology if you are being coldly scientific. And fiercely protective and proud of the next generation that you have successfully reared. I know the overwhelming sentiment of it.
And don't forget, you will always see in your minds eye, that wee scrap of humanity that they began as in your arms, helpless and tiny. My son is over 182 cms now, but started his first day as less than 2 kgs in weight.

That was just love. No need for any other explanation. X

I love having my stepson home for awhile after graduation from university. I missed his size 13 shoes at the door. I love that galoot like my own. And I've never forgotten the fierce and surprising love I felt for my firstborn when she came into this world, either.

Parenting is very primal and its mechanisms are deep in the wiring given us by natural selection. It "feels" more mystical than that, but that doesn't make it mystical -- or less meaningful, either.

I know of this feeling you are talking about. I am so happy for you. Enjoy enjoy enjoy.