I was curious about this. What is the relationship between the Tataglia who held down Luca Brazi's wrist while he was knifed and strangled and the Tataglia that Vito made up with at the conference Barzini put together? Was the first one the son that Sonny had killed?

yes, that was Bruno

the father at the meeting is Philip

The guy in the club with Sollozzo and Luca is Bruno, who was killed by Corleone buttonmen when Sonny got mad after McCluskey broke Michael's jaw at the hospital.

The Tattaglia at the meeting of the Families is Philip Tattaglia, the head of the Tattaglia family.

Was Bruno's hit a result of McClusky breaking Mike's jaw, or was in retalition for the attempt on Vito?

They knew if they took Sonny out of the picture, then they would defeat the Corleone family as they thought Hagen would be inadequate since he is not even sicilian and they didn't consider anyone else in the family to be able to wage war against them. They underestimated Vito's strength and health, as Vito hearing the news pulled himself together so he can save the family from certain destruction from the enemies.
Sollozzo is not really a Tattaglia as he's allied with them as business partners, since the Tattaglias would be doing the operation procedure in the drug business, Sollozzo was setting up.

It was in retaliation for Luca being killed,and a little of Vito being shot. Hell, with Sonny, it could have been because when he stepped on a bug,it squirted on his shoe.

when mike was hit, i think sonny got pissed of and whanted to get back ,

don fredrico