I agree w/the poster who stated that your Nanny Family may have used your #SSN + good credit score to obtain two credit cards in your name.
They likely thought that they would be able to get away w/it by having the statements sent to their own address.
I would directly ask them if they could give you an explanation as to where these other two credit cards came from since you only use one.
Also, explain to them your unfortunate situation at how your credit is tanking & see what they think.
If their answers do not satisfy you, make sure you actually have some proof to accuse them of identity theft.
For example, since you haven’t used those two other cards yourself, then that can easily be proved because you wouldn’t have personally signed for anything purchased on them.
It likely will have a paper trail leading back to your employers.
If that turns out to be the case, then the credit card companies will do an internal investigation + let you know their findings.
Then they will let the credit bureau know you are a victim of identity theft and your credit score should be back to what it was.
Obviously you will no longer be able to continue working w/this family for obvious reasons.
Hope you find all this useful.
Good luck.