“Can you believe your baby is turning 21 tomorrow?” the daughter proclaimed rhetorically in a phone call last night.

“It is truly amazing,” I responded. And, my dear, you’ll never know just how amazing until you have a 21, 23 and 25 year-old of your own.

Today, as my favorite youngest child turns legal, I can’t help but think about what life would have been like without him.

When we were young and in love, my spouse-to-be and I were certain we wanted five children. We named them before we were married: Max, Molly, Eric, Sophia and Abbie. They’d all be born two years apart and once the youngest was diaper-free, we’d start toilet training a puppy. His name would be Winston.

As perfectly planned, first came love, then came marriage, then came Molly in the baby carriage. Max followed 22 months later.

I knew the spouse was beginning to dither when our conversations started going something like this:

Me: “When Eric’s born…”

Spouse: “You mean AIR – IK.”

Me: “No. Err-ick.”

Suddenly, proper pronunciation was becoming an issue.

When I cleverly switched out Eric for Phillip, the truth came out.

“You sure we should have another one?”

And the ever-sensible spouse tossed out reason after reason why we’d be better off leaving well enough alone. We were just fine with happy, healthy Molly and Max.

But, I dug in deep and countered relentlessly with a dozen reasons to have just one more.

Of course, I won. Leo came along in a timely fashion, gracing us with a four year-old, a two year-old and an infant. And though his arrival took us from a family of four riding the Tilt-a-Whirl to a family of five riding a 21 year-long roller coaster, it’s certainly been well worth the extra tickets.

So, when anyone asks me if they should have a third child, I answer with a resounding and unequivocal YES. And while there will always be viable arguments for not having a third child, the reasons to go for it far outweigh them all.

1. Just as the rule of three is used in interior design, it is equally as important in the inhabitants of your home. You always need something to skew the balance.
2. If you’re given a boy and girl as Numbers One and Two, you’ll want to know if their personality differences are gender-driven. You won’t know for sure until you have two of one kind. Conversely, if you begin with two of the same sex, and go for three, you just might get that coveted boy or girl. The problem arises when you don’t stop trying until you end up with four boys. Or worse, four girls.
3. Everyone needs one child who doesn’t provide an itemized birthday list. The third child is so used to going without that when he says, “I don’t need anything,” he means it.
4. The third child has learned from his siblings before him. He knows not to ask permission for things to which his parents will say no. Instead, he just does as he pleases and deals with the consequences later. Of course, there are none because he is the third child.
5. Every parent deserves to raise one kid without worrying if he has eaten enough, slept enough or drunk enough. Though long before that last one sees the light of 21, you know that under-drinking was something you really didn’t have to worry about.
6. By the time number three gets to college, you’ll be rich enough to be able to pay his tuition in cash. A myth worth holding onto as long as you possibly can.
7. Three kids will help you win the let’s-move-to-a-bigger house argument. And though that bigger house will completely eradicate the college savings fund, the years of a friends-filled basement and a bottle-filled attic will make every one of you way richer.
8. Having a third child ups the odds of getting a call about a legal infraction from the high school principal or the local police.
9. The third child will successfully dispel any traces of Superwoman Syndrome. It becomes abundantly clear that it is impossible to be in two places at one time. Or with two children at the same time. Because each will have his or her own place to be. On the same day. At the same time.
10.  While Number Three certainly shifts the balance of power, it also gives you a built-in excuse for why you’ve become powerless.
11.  Number Three gives Number One and Number Two another person to fight with. And fight for.
12.  Having three children will increase your chances of raising one who will take care of you when you’re old and feeble, one who will talk to you about their deepest fears and foibles and one who won’t move to another time zone.

And, no matter how stretched you were with Numbers One and Two, when Number Three comes along, you realize that you did indeed have another thousand readings of Owl Babies left in you. That no matter how many times you’ve been through it and how much you’re looking forward to it, you still get that old familiar lump in your throat when Number Three walks for the first time and speaks his very first word. When he gets on the kindergarten bus with that heart-wrenching look of trepidation and brings home his first drawing of the family – with Mom dominating the whole page. When he strikes out for the third time in one game and when he ends his Little League career with a grand slam homerun. When he shares his dreams and when his nightmares kill them. When he finally asks for advice and finally takes it. When he gets dressed up for the prom and when he packs up for college.

Yes, that old familiar lump hurts a little harder with Number Three. Maybe it’s because you know that it’s the last dance. That there’s no one coming up behind him. That while your kids have been your whole world since the day they were born, you know there’s someone out there just waiting to become their whole world.

And so, you just raise them up and let them go. And know that the best thing you ever did was to have Number Three. Number Three, who by no fault of his own pushed your limits, tested your strength and tried your patience. But, at the same time, completed your family and tripled the size of your heart.

Cheers to you, Number Three, on your 21st Birthday!