Lucy's family is about to change. They're having a baby! Actually, her mom is having the baby. But when the baby arrives -- whether it's a boy or a girl -- everyone's life is going to be different.

The oldest children are the twins, Marty and Ellen, who are in fourth grade. Then there's Lucy, who's not even in school yet, plus mom and dad. Things work out pretty well at the moment; each child has a separate room. Their parents both work. Lucy goes to day care, while the twins stay after school for the extended-day program. But where will they put a baby seat in the car, and will there be room for a high chair at the kitchen table?

What will happen when the new baby gets here? "You'll love the new baby," their mom tells them. "Babies are so cute and cuddly."

Cuddling a baby sounds okay to Ellen --

although she doesn't like to think about changing its diapers. And it's going to cry all the time. She remembers when Lucy did that.

Lucy doesn't seem to like the idea of the new baby at all. "When that baby comes here, I'm not playing with it," she says. "Not ever!" And she sounds really mad.

You might think that Lucy's being mean, but what she's feeling is normal. If you have younger brothers or sisters, you probably had angry feelings about them, too, although you may not remember that now.

Researchers have studied how older siblings feel when new babies are born. Many studies show that the older you are, the easier it is for you to understand and adjust to the new arrival. But even when you're older, you're likely to feel jealousy and resentment. You may even feel scared that your parents will love the new baby more than they love you.

Marty has only said nice things to his mom about the new baby. But inside he's a little worried. "The baby is going to be awfully tiny," he thinks. "It'll take all of mom and dad's time. I'll be stuck taking care of Lucy."

Lucy doesn't think about the new baby the way the older children do. She just acts more childish a lot of time. She acts like a baby herself. And she loses her temper a lot. Once she even punched her mom's growing tummy.

"I guess you're wishing that there wasn't any baby inside me," Lucy's mom said when that happened. Then she talked about what it was like when Lucy was born. She held Lucy on her lap and cuddled her. Lucy seemed to feel much better afterward.

Their mom also explained to Marty, Ellen and Lucy that the new baby will take up a lot of her time at first. She warned them that the baby will be too little to play with. But she reminded them that she will still love them just as much as she does now. "Don't worry," she says. "Dad and I have more than enough love to go around."

When a new baby arrives, people's feelings can be confused for a while. A young child like Lucy might feel she has done something wrong. "If I were good, they wouldn't need to get another baby," she might think. Older children may worry that their parents aren't interested in them any more now that a brand-new baby is around. Even fathers may feel uncertain. "My wife loves the baby more than she loves me," they might think. And then they feel bad for thinking that.

Psychologists -- professionals who study human emotions -- say that all these feelings are quite natural. And bad feelings tend to be mixed up with good feelings about the new baby, which can get really confusing. But don't worry; as the family adjusts to the new arrival, everyone will settle down.

Here's what might happen: Lucy will discover that she likes to coo and sing to the baby and watch it fall asleep. Marty will feel very grown-up because his mom lets him hold the baby. Ellen will enjoy reading bedtime tales to Lucy and the new baby. They'll discover an added bonus: For six months, their mom is going to stay home from work. They'll get to come home early from preschool and school and play in their own house all afternoon. Their dad will forget that he ever felt worried about not getting enough attention with four kids in the family instead of only three.

After a while, it will be hard to remember what their family was like before the new baby was there. When they look at their new baby, they'll love it. After all, it's a whole new person -- someone they're going to know and share things with for the rest of their lives!

Tips for Parents

Reading books together can help prepare a child for the arrival of a new sibling. Two good ones: "That New Baby: An Open Family Book for Parents and Children Together" by Sarah B. Stein (Walker & Co.) and "Peter's Chair" by Ezra Jack Keats (Harper & Row). And these tips from the just published "The Preschool Years: Family Strategies That Work" by Ellen Galinsky and Judy David might help, too: Arrange for your older child to visit you at the hospital. Take photographs or movies of your older child meeting the baby. Give your child a present because now he's a big brother or she's a big sister. When friends and relatives visit, see that the older child is not ignored. Make sure guests pay attention to the older child. You might suggest that they bring something small for the older sibling if they're bringing a gift for the baby.

Catherine O'Neill is a children's writer.