SEO and whois information
 

Let's say you have different sites / domains on different webhosts with different class-c ips and you interlink them but all your domains have the same whois information. Will the search engines know that those domains are all yours and penalize you for that?

The last I heard, there's a lack of evidence as to wether google (the only se to which this concern really applies) was using whois as part of it's ranking algo.

Definitely it's part of their investigative and human review toolkit, if for some reason they look at your domains manually.

The basic ranking algo can detect the interlinking, wether or not it checks and ranks with whois.

So, you're fucked coming and going.

How else are they going to detect reciprocal linking?

There's no factual evidence but if I were you I would protect your whois or else remove some of the crosslinks (if you're talking about 2-3 crosslinks I wouldn't worry). Stuff like that may not lead to penalties unless your tactics are excessive but it can diminish Google's trust in your backlinks and your forward links. Personally, I don't link out from my main site to any of my lesser domains.

What if I use different (first name) family names for different domains? For example one domain owned by Bill Clinton and another one owned by Hillary Clinton but they live at the same address? Or same name but different address?

I have two real addresses in two different countries for example. If I use my real name but different addresses for the domains would Google still connect them?

Yeah why not?