Hi - we've faced the same issue a few times. Usually they only have two seats available in biz, but on some flights/dates they do allow more than two. I was recently able to book three award seats for the family in biz for AUH-DOH. Granted its not their busiest route so that may have helped.

In other instances, I've booked the two available for biz, then bought economy for the other two and used miles to upgrade. Its the next best option.

Hope that helps!