This is a great and mentioned The Whole-Brain Child which was co-authored by Dan Siegel and Tina Bryson.

Below is a cut and paste from the original article:

Q: My twin boys will turn 5 soon. They're great, bright, normal kids (backed up by their preschool teachers), but in my mind, 5 feels like the transition from toddler to kid, and I'm afraid I'll start expecting too much of them. For example, they aren't especially interested in learning their letters, which I've been figuring they'll come around to when they're ready, but I'm afraid that when they're 5, I will start worrying and push it too much. Can you give me an overview of what to expect from active 5-year-old boys?

A: I have never raised twins, but from what I have heard, you have made it through a pretty tough (but exciting and fun ) couple of years. Two toddlers throwing tantrums , two toddlers whining, two toddlers running in opposite directions, two toddlers giving you sticky kisses and two toddlers to cuddle. And now they are in preschool! Developmental changes are afoot , but I am not sure why you are panicking now. Is it because this feels like “real school”? If that is the reason, I don’t blame you. Schools in the United States are moving toward more rigorous standards in the younger grades, which can result in unreasonable learning expectations .

[I’m a mom of twins. The movie ‘Three Identical Strangers’ changed how I parent them.]

In general terms, 5-year-olds are coming into their own. You may find that your boys are more empathetic and kind to others, but may also accuse others of cheating if they lose a game. Children this age love to play and use their imaginations, but these imaginations can also scare them. You may find that your boys are sharing their newly found opinions often and loudly, and that they cannot be fooled or manipulated into moving on from a subject or place easily. With this stubbornness, you also can get defiance that does not disappear with punishments; instead it worsens. Parents also find that their 5-year-olds enjoy potty humor, and storytelling can be imaginative, funny and (sometimes) boundary-pushing. Five-year-olds love to have real work that means something to the world and the family. And because their attention spans can last a bit longer, they can focus on more complex projects and instructions.

Even though your twins may appear to be mature at times, ­
5-year-olds still have tantrums, resort to violence and call people names. If the school days have been long and their nervous systems are taxed, you will find a 5-year-old regressing into 3-year-old behaviors. This is completely normal.

As for what to expect from active little boys, our culture loves to think that boys and girls are opposite, but their brains are not as different as people imagine. Boys’ brains tend to excel in visual-spatial integration, while girls’ brains excel in reading social cues.

What does this mean for your twin boys? It doesn’t mean that a girl cannot be coordinated and that your boys cannot be highly verbal. Instead, it can show how, if a boy’s brain excels in spatial issues, his body longs to jump, climb and test out the space around him. It also tells parents of boys to do (at least) two things: Let the young boys move frequently, and use emotionally expressive language with them.

Because 5-year-old boys typically love to move, most educators and parents focus on getting them outside and into activities such as soccer and karate. I encourage more movement for all children, especially during school hours. But just because boys’ brains quickly assess spatial relations doesn’t mean they don’t have a need for us to model and use productive emotional language with them. Parents can use phrases such as, “I felt really frustrated that I got stuck in traffic today, and because of that, everything got tough at work. I was angry about it for a little while, but I took a walk and cooled down,” or, “You’re sad that we ran out of cookies; I am, too. It really stinks, doesn’t it?” This has a huge impact on all children, especially boys. Even the simplest show of emotions can help a 5-year-old express and regulate his feelings.

Remember, development is not a steady climb uphill; it comes in fits and starts. For instance, one of your boys may begin eating like a horse, napping again or acting more agitated, and you may think, “Wow, Ralph is getting sick,” or, “Ralph is really being out of control.” But what is actually happening is that he is in a growth spurt. Like being in the eye of the storm, you cannot see the whirlwind around you until you are out of it — or in this case, until you go to your pediatrician and the doctor says, “Ralph grew three inches!” It’s not easy having two boys around the same age with their own developmental road maps. So be kind to yourself. Practice asking, “What is this behavior really about?” when you find yourself stumped.

Finally, don’t forget the power of connecting to each child as an individual. Maybe it is roughhousing, maybe it is cuddles, maybe it is foot rubs, maybe it is walking around the block, or maybe it is reading together. Just be prepared to continuously reach out to both children with love, especially when they are moody.

For books, I would begin with “The Whole Brain Child” by Dan Siegel and Tina Bryson. I find their explanation of the child’s brain and how it relates to their behavior to be clear, nonjudgmental and science-based.

Good luck.