Blake Lively and Eva Mendes Credit: Rob Kim/; Angela Weiss/Getty Images

Blake Lively and Ryan Reynolds’ daughter, James, 16 months, is in for a surprise: She’s going to be a big sister! And Eva Mendes and Ryan Gosling’s little girl, Esmeralda, 19 months, is in the same boat. (Us Weekly exclusively broke news of both couples’ pregnancies last week.) Susan Stiffelman, a licensed marriage and family therapist, shares with Us Weekly her top six tips for transitioning the only child to older sibling.

Manage your child’s expectations “Don’t promise your youngster that he is going to love the new baby — he may not at first,” the author of Parenting Without Power Struggles tells Us. “Best to avoid setting him up for guilt if his initial reaction to the baby doesn’t match up to the idealized picture you painted of unbridled joy of his sibling’s arrival.”

Manage your own expectations Stiffelman says a child is likely to have a wide range of emotions about the new addition, from curiosity and fascination to resentment and jealousy. “New babies require everyone to make big adjustments, and those take time,” she notes. “Don’t set yourself up for disappointment if your older child isn’t all angel hugs and butterfly kisses toward your new little one.”

Stick to routines According Stiffelman, children do best when life is predictable. “Try to maintain homework, bedtime and mealtime rituals,” says Stiffelman, who penned Parenting With Presence. And keep the same rules you had before baby: No brownies for dinner to soften the guilt you feel for shortchanging your child on attention!

Keep the mood light  “One of the best ways to manage big feelings is to laugh and play,” the Malibu-based therapist says. Her suggestions: “Talk in a goofy accent when you feed the baby! Have a pillow fight!”

Allow him or her to vent “Your older child needs to know that it is safe to feel both excited and unhappy about her new sibling’s arrival,” explains Stiffelman. “If she hints at being less than enthusiastic about the baby, don’t try to talk her out of her feelings. Instead, acknowledge and validate: ‘It sounds like you want to meet your new baby sister and you’re worried that Mommy might not have as much time for you. Did I get that right?’”

Encourage visitors to fuss over the older child Says Stiffelman: “Ask relatives and friends … to make a point of acknowledging your older child by asking questions like, ‘What is it like for you to be a big brother, Sammy?’ Or, ‘It looks like your baby sister can’t take her eyes off you, Sarah.’”

Want stories like these delivered straight to your inbox? Sign up now for the Us Weekly newsletter!