Science fiction novel over 10 years old....?

there was a series of sf paperback, thick books, exciting covers showing characters...the first in the series had an intergalactic conference and introduced numerous character who were all killed around page 80. The royal family had had three or more sons. All but the youngest were killed. The successor was a ne'er do well who went joy-riding in his space ship and missed the conference and the massacre. I thought the author was Sherwood Smith but it's not. Please help!