There are many reasons that children may cry or otherwise behave upset. The exact reasons for this depend a lot on their age. So it is hard for me to say specifically without knowing the ages of your children.
However, generally, I think it is safe to say that most children who cry or act out do not have a serious psychiatric problem like depression
. Rather, children cry in order to communicate their frustration or need (infants, for example) when they cannot talk As children get older, they may also cry to manipulate their parents or get something they want. This happens naturally, as children are very good observers of their parents' behaviors and they learn how to use their own actions to evoke a parental response.
This dynamic is the source of "temper tantrums." The best approach to temper tantrums is to remain calm and not to make a big deal out of them, either positively or negatively. This way you are teaching the child that crying will not produce the results they are looking for. A positive but firm and consistent style of parenting can help you get through this difficult phase of the child's development.
Talk to your pediatrician
if you have more questions about your child's behavior.