Multiple Domains On One Droplet

Using digital ocean, is there any reason why I should or should not have multiple domains on one droplet? The two sites are affiliated (sister companies) with each other and will link out using keywords.

The cost to create a droplet for each site is really minimal, so I’m not interested in saving a few dollars on hosting monthly.

I’m just trying to understand any benefits or disadvantages, but my instincts are telling me to keep them separate.

don't put all your eggs in one basket

I think you should keep them separate. If one site goes down because of some problem, at least the other one will still be up.

If you are going to have everything in one place you need to think about backup seriously.

Sure you can add as many as you want.
Just always backup your sites, ( for example to dropbox).

For example i have server and hosting 25+ projects on one server.