Kids! Come here  -- it's important," my husband calls. Henry, 6, and Eleanor, 4, clamber onto the sofa, looking vaguely worried that some long-forgotten transgression has just been discovered. Spilled juice behind the cushions? Yet another unflushed toilet? Margaret, almost 2, obliviously sucks her thumb.

"Guess what! Mommy has some big news to tell you," Daddy continues.

Everyone leans forward, but before I can say a word, Eleanor speaks up, eagerly: "Is Henry moving out?"

So much for sibling revelry.

There I was, excited to tell my daughter she'd be gaining a new brother or sister in a matter of months, and there she was, hoping to ditch one.

I immediately thought back to when we told our beloved firstborn  -- the light of our lives  -- that he was about to become a big brother. "You got a ball in there for me?" Henry, then 20 months, had asked, peering under my shirt. Saying no, I'd felt like a traitor. A friend once told her daughter that come Christmas, she'd be getting "a new, teeny-tiny baby." The toddler looked her square in the eye and said, "No thanks. How about a new, teeny-tiny puppy instead?"

Uh, sorry.

Sibling relationships are complex from the start. There are classes and self-help groups galore on dating, marriage, divorce. Shrinks love to focus on the parent-child bond. Grandparents' rights are hotly debated. But the ties and feelings that are unique to siblings simmer along, largely unexamined. You don't pick your brother or sister. You have no particular obligation to this person (other than "Be nice"). Although you share genes, Mom and Dad's household rules, and maybe even hand-me-downs and bedrooms, you may have little in common.

Yet you're thrown together endlessly. And naturally you each want, desperately, the same thing: your parents' undiminished love and attention  -- an impossible quest that pits you against your siblings even as you depend on one another for support, entertainment, and companionship. "Can't live with you, can't live without you" is how my grandmother puts it.

"I hate you. Hey  -- where are you going? I wanna come" is what my kids say. I've known people who put off having a second child because they couldn't bear to take anything away from their beloved number one. But what we sometimes forget is that having another child is not about dividing the firstborn's allotment of love. It's about giving him more.

Now  -- after four kids  -- I no longer feel guilty about having inflicted siblinghood on my babies. Instead, I feel confident knowing I've given them the following:

Contributing editor Paula Spencer wrote "Your Baby's Big Triumphs," in the April issue.

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