3 years old is a hard age. For them.
For them.
When I was preggers with my 2nd child, my daughter was about 3 years old. And, while... I was pregnant with my son, I spend a lot of time, bonding with my daughter and chatting with her, about baby brother in my tummy. She'd sing to him, rub my tummy, we'd take photos of her and my tummy etc. And it was a pleasant thing for her. Because, I chatted with her, about it, BEFORE her baby brother was born. I also explained to her, in ways she could understand... what would happen once her baby brother was born. ie: he is a baby, he will cry, Mommy will take care of him and nurse him... JUST like how I did with her. Babies don't know how to do things, and they cry anytime etc. But don't worry. AND I am ALWAYS there for her.... and she can TELL ME her feelings, and she need not feel she has to be OLDER just because she is the "oldest." That I KNOW... she is just a little kid herself. And I WILL NOT EXPECT... her to be "perfect" and she is still, just my little girl. I explained (because kids worry about this) that "her" things does NOT have to be shared... and if she has special things, to just tell me. And she can TELL ME, what things she wants to share, or not, with brother. Its OKAY.
I fully explained to her.... before her brother was born... about how she is herself, and I know that. But Mommy will be busy with baby... but she is important too. I told her I will be nursing baby brother a LOT. And so we made up a special hand signal & wink with each other, and even if I was nursing, she and I could do that with each other, even if she was across the room, and it was OUR way... of bonding and for her to feel close, to me.
And I made SURE... to comfort HER, when she needed it. Because, I made sure, that she KNEW.. that she could tell me how she felt, anytime... and it was okay. I told her that I know, she may have hard days too... and its okay. To just tell me. That Mommy loves her and she is always, my little girl.
I spent a lot of time, PREPPING my daughter, while... I was pregnant with my son. I spent my pregnancy, for my daughter, and prepping her... for her baby brother.
So, when her baby brother was born, and came home... she adjusted FINE. With no hang ups. And she was a champ, at being a sibling and adjusted, so well. She never had any jealousy, toward her baby brother.