Question 883337
If you disregard the problem of the 
brothers not sitting together, there are
{{{ 8*7*6*5*4*3*2*1 = 8! }}} ways
From this you can subtract all the ways 
the brothers can be seated together
------------------------------------
B B * * * * * *
* B B * * * * *
* * B B * * * *
* * * B B * * *
* * * * B B * * 
* * * * * B B *
* * * * * * B B
There are {{{ 7 }}} ways they can sit together
so, the answer is {{{ 8! - 7 }}}
You might get a 2nd opinion, but
that's my guess