Between Credit Karma and Experian everyone should be monitoring their credit and their family's credit for free already. If you aren't...
Credit Karma to monitor Equifax and TransUnion. Ignore the FAKO score ("fake" FICO, they use a weird calculation banks and cc companies don't use so don't freak out about your "score"), turn on alerts and you'll get an alert every time your credit is hard-pulled or a new credit account is set up for EQ and TU. You will also get alerts when you pay your cc sometimes so that's annoying but worth it for the other alerts.
For Experian you can sign up with them for free to watch your EX account yourself with alerts, they have an app. (They'll keep trying to get you to pay, don't) like with Credit Karma you'll get alerts when your credit is hard hit and accounts are opened/closed.
I've found both very quick to notify me when hard pulls occur and account openings/closings hit my credit reports.