Question about domains and addon domains

Hello guys, sorry if this is a simple question, but I can't seem to find the answer.
I apologize in advance for not knowing all the correct terminology to explain in detail, I'll do my best

Basically, I started a baby plan with hostgator with a single domain, and over time, I added on a couple other domains, but the primary domain on the account is the first one I used. When I look in cPanel, I can see all my addon domains, but they are also listed in my subdomains too.
For example in my addon domains, I see:
domain2.
domain3.
domain4.

But in subdomains, I see:
domain2.domain1.
domain3.domain1.
domain4.domain1.

Is this affecting my SEO by creating duplicate content? If it is, can I fix it by simply redirecting them to the home domain?

Thanks for any help,
Kris

You can redirect them to the main domain via .htaccess - use the file manager to create one, then copy a .htaccess with a redirect from the www.

Some hosts show these and some don't. The main place I remember seeing these is when you go to make email accounts. You don't need to do anything, just ignore them. Now that I think about it, I think it was hostgator that had those.

yep, just redirect them and there will be no duplicate content. If you can't deal with .htaccess you can do it in cpanel too.