Technically, the username should be able to be transferred over as a secondary account under your relative's account, but in reality it's really a huge headache to do so using Einstein (Comcast's internal tool for agents). Sometimes you get random errors about failures for some obscure reason that you have no way of fixing and you really can't do anything about.

For example, there's something called a transfer lock that has to be enabled on your username before it can be transferred. So, I switch over to your account and enable the transfer lock for your username. Then I switch back to the destination account and try to transfer it over. Best case scenario it works, probably not though.

The next headache is if that username that you're trying to transfer is the primary username on the old account and/or it is the only username on the old account. In that case you have to go and do something like create a second username and then make that username the primary on the old account in order to proceed, which takes a few minutes at the minimum to get done. Agents are rated based on their average handle time, and if they take a long time on a call they'll get supervisors asking questions, so they are not inclined to take their time to help you out.

Then finally after you get all that done and you try to transfer the username, it'll give you an error message saying that the username is already taken or something similar, even though you're just trying to transfer it and not trying to create a new username. So it's all just a huge waste of time.

This is from direct experience and all from memory, by the way.

If you're really adamant on getting it back and activated again, I'd try and take the path of least resistance, see if you can get the account activated again temporarily by the billing department so that your login works again. At that point, I would immediately export all of my emails and needed information, and afterwards just call back and cancel the service.