How can I combine two public keys to create a joint address?

Question

I'm trying to create a new address that either Alice OR Bob can spend from.

Is there a tool or library I can use to accomplish this?

At a high level:

• I'm taking (AlicePrivateSpend + BobPrivateSpend) to make JointPrivateSpend

• Multiply by G to get JointPublicSpend.

• Repeat this to get public/private View keys.

• Create the Monero-variant Base58 encoded address.

To test, I go to the wallet and try to recover from keys. The joint address cannot be verified.

I verified that my address encoding is working OK in two different libraries. The problem is in my key generation, which I can elaborate on with code snippets if necessary, but the root of the question is, does this library or code already exist?