Croats came on Balkan in 7 century AD. They are slavic. Same as Serbs. But Serbs came earlier in 5 century AD. Before Ottomans in Bosnia ,according to Chatolic church, lived 700 000 Croats , 30 000 Serbs and 30 000 Bogomils. When Ottomans came Bogomils took Islam. Bosnians separate. In 13 century is first time of usage of name Bosnian as I remember. Anyways from Ottomans started Birth of Bosnian nation.
We are mixture of Slavic (mostly) and many others (minority). Illyrians, celtics, Italians, Greeks, Huns,Goths....
Balkan was always highway for civilizations.
Oh yes, Bogomils were sect of Serbs and Croats. So Bosnian mostly became from Bogomils (Serbs and Croats) and
Who were also Serbs and Croats.
So there isnt Bosnian slavic tribe.
Only Croatians and Serbs. But now we have also Bosniaks nation. They are also slavic but separate from previous two when they took Islam.