Introducing Your Oldest To Their New Sibling
Introducing a new member to the family is a big deal, and can be both joyous and traumatic. For an only child to transition from the one and only to the oldest of the clan successfully, they are going to have to be introduced to the idea gently. Remember that when families expand it is never a straight line. Your first child might be in love with the idea one day, and absolutely horrified by it the next.
So what can you do as a parent to help them get used to your new family structure?

According to the Mayo Clinic, you should simply be realistic. Explain the concept of a baby in age appropriate terms, but do not let your first born believe that their new sibling will be a playmate right away. Explain that the new baby will eat, sleep, and cry just like they do, and encourage them to be involved in setting up the nursery. By including your child in baby prep and conversation, they will not be shocked when the new little life arrives.

When you do finally give birth to a new little brother or sister, have a trusted relative or loved one bring your oldest to the hospital. The Mayo Clinic also suggests purchasing an older sibling gift that you give to the oldest from their new siblings. This will help to inspire feelings of gratitude and affection, and will break any tension that your oldest may feel.
Basically, stay positive, but realistic. The worst thing you can do is to extol the virtues of your new child without warning your oldest about any of the challenges of having a baby around. If you prepare them gently and over time, they will be more than prepared to handle the emotional rollercoaster that is a new baby. Remember, it isn’t just about you and your partner this time.