Aggregating Multiple Private Keys Under the Same Seedphrase

So I was wondering if there's any way to combine multiple, unrelated private keys under the same seedphrase (each one was generated via a different seedphrase)?

Basically I have 3-5 primary defi wallets that I've accumulated over the years (and still use) but whenever I have to switch wallet providers or update an app it's pain in the ass to backup since I have to keep track of multiple private keys rather than just backing up to 1 seedphrase. Is this even remotely possible?