Defining a genealogical relationship

I think the people at Geni have played one two many games of Degrees of Kevin Bacon and are confused about what it means to be related.

They say William Shatner and Leonard Nimoy are related.

This is not a genealogical relationship:

One might be able to call it a legal relationship. Though once you get beyond one set of in-laws I suspect that is questionable. And since there is one "ex" involved in the chain, the legal relationship that was created was also dissolved. Legally. Regardless, Geni isn't supposed to be a legal site. It's supposed to be a genealogy site.

If we accept legal relationships in genealogy, do we accept census definitions?

• Are POSSLQs relatives? The US Census Bureau created the term. A relationship created by the US Government has to be considered a legal relationship.
• Is a female who was in the same dormitory as me in college a POSSLQ? Were we related? Are we still related all these years later? Do I need to tell my wife?
• What if, instead of a dormitory, it was a group house?

Yes, my wife and I have adopted twin sons. I don't claim a genealogical relationship with them. A legal relationship. A loving relationship. Not a genealogical one. When they grow older they may well 'adopt' my ancestors as their own, as many adoptees do. But the relationship will be one of the heart, similar to when someone refers to a friend of the family as "Uncle Joe" or "Aunt Jane." One doesn't expect to see these relationships on a genealogy website either.