Mamesh a wonder.....
The gemara in Yevamos quotes Beis Hillel as learning that one must have a boy and a girl in order to fulfill the mitzva of procreating from the pasuk זכר ונקבה בראם- "[Hashem] created them male and female." That is LOVELY but what does the fact that Hashem created "male and female" have to do with us lowly humans?
Maran HaRav Hutner Ztz"l: We must seek to emulate Hashem in all of our middos but in His middah of being a creator ex nihilo - יש מאין - something from nothing, we are quite limited. We can't create ANYTHING out of thin [or even thick] air. The CLOSEST we get to creating something from nothing is having children. Think of the MIRACLE. A putrid drop of semen meets up with an egg and that develops [all by itself!] into a living, breathing, thinking [unless he spends all day on Facebook], talking, human being. Remarkable. A drop of nothing into an Einstein or li-havdil a Vilna Gaon. [To my mind there is overwhelming evidence of the existence of G-d but if all there was to indicate this was the reproductive process that would be enough to convince me that He is there - and here. The atheists say "An accident". Amazing how that "accident" is so beyond complex and defies the imagination....]
So if Hashem created a male and female and we share that creative ability [to a certain extent] with Hashem, that obligates us as well.
Under the chuppah we say המקדש ישראל ע"י חופה וקידושין - Hashem sanctifies us with chuppah and kiddushin. Hashem "married" klal yisrael with chupah and kiddushin and we emulate him by marrying with chuppah and kiddushin. Kedusha is the one middah where the Torah explicity commands us to be like Hashem. והתקדשתם והייתם קדושים כי קדוש אני - You should be holy because I am. So when we marry a woman with קדושין we are walking in the footsteps of Hashem and of course it follows that the mitzva of having children is also going to be the highest expression of imitatio dei [emulating Hashem].
Yes, friends. Two Latin expressions in one post. Impressed??:-)
PS - Great is learning when it brings to action:-).
עפ"י עולת יצחק עמ' שח