Private keys you mean, is it seed phrase or passkeys for custodian or non custodian network to be precised?
If you mean seed phrase of decentralized networks and you have lost access to your wallet, you can not recover it. That is why we must be always more conscious with our private keys.
But paraventurely you mean the centralized network, then you can always recover it with your backup contacts. Probably by email or phone number.
Private key and seed phrase are different.
Private key is one string that can be either contain 51/52 characters in WIF format or 64 characters in hex format. While seed phrase are using words and could be vary, usually 12-24 words.