I'm doing a research for conceptual Logodesigns which should fit into a ecosystem.
I'm not sure if logosystems, ecosystems or logofamilies are the right terms.
I'm thinking about logosets like the Adobe Creative suite or the logofamily of the wikipedia foundation. Do you know any other Logofamilies like these two examples?
Family is a correct-ish term. There are various substitute terms available to describe branding and the many types of branding, but they all follow a general structure. The following infographic is a simple yet powerfully obvious example of some of the different types of brand sets (for want of a better term):
Taken from a report about managing brand architecture strategy when extending from B2B to B2C
Depending on what you're looking for, there are a lot of ways to achieve harmony in an ecosystem of products and/or services. As JohnB said in a comment and as you note, Adobe Creative Suite and Microsoft Office are great examples:
An example that came to mind was the case where sports blogging network SB Nation redesigned their logos. Below is a sample, but I encourage you to visit the post to see how disconnected they all were before and how unified they look now:
Logos are kind of like Icons
Icons are a lot like logos in terms of the design process. With logos, you're trying to reduce a brand, an idea, a product into something that's simple, memorable, and flexible. With icons, it's a similar story. So when a commenter pointed out that the SB Nation logos reminded him of Foursquare badges, he makes a good connection.
Therefore, it might be worthwhile to check out some icons families, like this one designed by Susan Kare:
An image on Wikimedia provides a nice infographic on the icon design process (Here's a link to the author Andaja's page...not sure which link will stick around longer.). I reference it for this particular part:
So, logos or icons that share a color palette, or a type of perspective, or a certain degree or method of abstraction will look more unified.
Identity is more than logos
Sometimes the logo stays the same, but a unified ecosystem can still be created by other means. XL Insurance is a great example:
A final great example is when Nickelodeon rebranded. See how they went from logos that were pretty scattershot to a set of brands that were well-integrated: