I have a 2.5 bathroom house, 2 full upstairs and a half down stairs... and I have a tri level home. The bathrooms up stairs basically sit back to back against the wall. The one my bedroom sits to the back of my kids bathroom. Every time my kids flush there toilet the water in my toilet decreases and I hear a gurgling sound in my kitchen drain... What could be causing this.

You have blocked vents. The discharge from the kid's toilet is setting up a suction that is pulling air through your toilet to vent the system. The gurgle you hear is air being put to your toilet. The solution would be to snake both lavatory roof vents.
If, however, you find that you have only one main vent that vents both bathrooms click on back and tell me about it as the solution will be different. Let me know how you make out. Good luck, Tom