I write frequently about practical things that parents can do to raise up healthy TCKs. While I believe that all of those are important, there is one thing that all TCKs need to hear clearly and constantly. One thing that has to be present in order for anything else to be effective.
"You are more important than our work."
This is the deep, heart-issue for many TCKs that contributes to difficulty building healthy relationships, poor--or exceedingly good--performance in school and work, and even mental health disorders. I can give parents a million tools for helping their children adjust to a life overseas and to prevent common TCK issues, but none of that will be effective if the child believes in their core that their parents are more passionate about their work than about loving and parenting them.
I have talked with and read stories and blogs of countless TCKs who felt that they were far less important than the work their parents went overseas to do. Parenting was just a required, inconvenient task.
I would guess that if you asked the parents of these TCKs, they would be astounded that their children felt this way. They would say, "But we put them in the best schools!" "We took them to amazing vacation spots!" "We made sure they were able to bring some special toys with them when we moved!" and so on. While these actions definitely contribute to the child's feeling of being loved, they do not replace the need for the craved words, "you are more important than our work."
Because of the nature of overseas work, it is easy for children to perceive that the people their parent(s) moved overseas to minister to, or the company they went to work for, or the country whose military they serve are clearly the first priority. After all, those entities and people groups literally dictate everything about their life--even where they live! Though it may not be the truth, children can quickly feel that they are second place to the job that moved their family across the globe. Sadly, this belief can accompany them through life and into adulthood.
As parents, our first priority is to raise up the children that God gave us. We have a direct impact on who they grow up to be, their values, and their priorities. It can be especially easy for overseas workers, whose life and work are so interwoven, to let parenting take the back burner. Show your TCKs that they are so valuable and cherished and loved and that being their parent is your most important job. Then tell them, "You are more important than our work" over, and over, and over.