on the : could Kankuro and Sasori be related front-

It would be a little strange, because then Sasori would be related to Gaara (and Chiyo talked about Gaara's father and sealing the Bijuu in Gaara without even anything resembling emotion). They could be inter-related somehow, but I wouldn't go out on the limb that just because Sasori's family uses Puppet Jutsu and that Kankuro does also means they're all related...

I always thought the Puppets were the Sand's solution to not having many wild animals at their disposal for summoning. So far they've been the only Village to use puppets (Oro's Zombie Summoning of the previous Hokages is a little different, but I'd not be surprised to see the relationship between he and Sasori as having helped him develop that Jutsu), while Konoha ninja summon animals alot of the time...