Cell phone tracking

I just found out, on my phone, that my parents put gps tracking on my phone when I was 21 years old. More so, i know it was my step mom that did it. I am now 24 years old. The gps tracking has been going on for 2 full years. I know it's them that did it because the account name on the app is "wendus family", wendus is my maiden name. My phone is on my own plan, in my own name, my dad and his wife have never once paid my phone bill. Is this illegal for them to put gps tracking on my phone without my knowledge and consent?