As others said you cant merge two different YouTube channels nor transfer videos from one channel to the other. But there is a way, and you can do what you want if you follow these steps.
Note that this does NOT transfer the text of the video so you can copy/paste your titles and text description from one to the other.
1. Sign into your YouTube account using the original account, which I will call "account A"
2.Go to Video Manager
3.Click the Check box on the video in question
4.Click the ACTIONS drop down (above the videos) and select CREATIVE COMMONS
5.Copy the URL for your video (i.e. start watching it then right click on the video an select COPY VIDEO URL)
6.Log out of your YouTube Account
7.Log into your other YouTube Account, which I will call "account B"
8.Paste the address/URL of the video you are trying to transfer into the address bar of your browser
9.Click the REMIX THIS VIDEO link (just below and to the right of the video near Category License)
What are you doing here is you are setting your videos license to CREATIVE COMMONS, and importing it to your new Channel. You will have to again put up the info, but hey you have saved valuable time from uploading all the content again. :) Cheers to that!
If you still don't get it, just ask me personally, I would be happy to help you.