My Mort(budgie) so wants the attention of her brother Fergie(Cockatiel) but he just huffs at her and spreads his wings. However if they each have there own turf they will talk to each other happiliy.
That's often how it goes with budgies and cockatiels :) as long as they have their own space, they probably won't fight. They may even become friends!
I was at a bird show once and talked to a woman who had four cockatiels and one budgie. I grinned at her and said, "But the budgie's in charge, right?" She said, "Of course!"
Haha nice one! :D