Emotional development starts right at birth when your baby is put into your arms. This is the beginning of attachment. By understanding your child's emotional development, you can help to nurture it and make it healthy.
There are four types of attachment: secure, avoidance, resistant and disorganised. The one to aim for is a secure attachment with your child. A secure attachment is one where you're very responsive to your child's needs and you're affectionate towards them and they are happy to see you.
To develop this type of attachment, you'd need to spend time with your child and respond to their needs lovingly. Your child will grow up secure and confident in your love for them. This is the most healthy of attachments.
Empathy is another aspect of your child's emotional development. Empathy is the ability to put yourself into another person's situation and feel what they feel. At around 2 years of age when children become aware of others as separate to them, empathy emerges. As language develops, children will think, reflect and use words to respond to others' emotions. From 7 years of age, children will understand that how others feel can be different to what they say. They begin to understand the nuances of emotions. The ability to empathize at a deeper level and take on the perspective of others not present develops from 12 years on-wards.
All of this develops when you talk to your child about emotions. It's hard to be empathetic when they don't know what others are feeling. When your child is young, start labeling the different emotions that they're feeling and call attention to how others are feeling. By being an emotion detective, you'll help your child be more aware of it, have the language to express their own emotions and respond to others.
This is just a brief summary of children's emotional development. For more details and activities to do with your child to develop attachment and empathy, get the book that I co-authored with others. Each of us wrote a chapter on a specific part of child development. Get it below (my affiliate links):