Are Free! and Haikyu!! related? I've only watched Free! and Free!: Eternal Summer, but recently a friend recommended I watch Haikyuu!! and looking at images of it, I'm reminded of Free! a great deal.

The characters even look similar and they both contain a plot based around a sports team.

Are they related, or could this just be a coincidence?
Apart from being of the same genre and containing similar enough art style, I don't think the productions are related. 

Differences:


The authors are different (Masahiro Yokotani vs Haruichi Furudate)
The production studios are different: Haikyuu!! is produced by Production I.G, Free! by Kyoto Animation 
Haikyuu!! is shonen whilst Free! is mostly targeted at women.


Similarities:


Character style (but this could just be that the style of the characters has been found to appeal to their target market and chosen for this reason)
Exclamation marks in their title!! (but so has K-On!! and many other shows)
Sports genre


The similarities between the shows aren't really substantial enough to warrant a link between them, so I doubt they are.

[I thought that Chihayafuru (another sports title) was similar to Haikyuu!! also, but it also doesn't have anything in common, so I think this is just an art style that sports anime have evolved into]