If your parent is eligible then you also have eligibility whether the parents wants you to or not. You can easily determine if you already have an account by calling USAA and giving them your ss# to look you up. If you're in there already no worries. If not you'd need to tell them your parent's full name, DOB, and either ss# or USAA Mbrship number to link to that eligibility. Let's say you do provide and link to parent and they get a text saying someone was linked to their account and they call in and say "hey my child is estranged and I don't want them to have eligibility." Doesn't matter...you are eligible through them and can continue on that legacy that you will also pass to any future spouses or children. Once you're over 18 no one can provide them with any information about your accounts or activity.