Mia, if your son has the amazon app on his phone it could be tied to his dad's account. I have the amazon app and so does my 15yr old. Both of us use the same amazon account & we both get the same notifications when buying/making changes to the account.
Me: 35 husband:39 Sons 16 and 11 from my first marriage Twins 5 (boy/girl) Daughter 3 Affair bomb 2/27/14 He moved in with ow 3/13/14 OW kicked him out 6/15/14 4/2016 he seeks help for sexual addiction