+1
"Surprise" never works for me. I attack with one member of the party from stealth, and the other members just sit in stealth not getting into the initiative. Meanwhile all the enemies are taking turns despite "suprise", gank party member I initiated combat with, and the others are just sitting there picking their noses until they get detected.
What you can do in that case is instead of taking your turn with the character who is in the active fight, select character(s) who are not in the fight, then get them into the fight.
I run across this situation quite often when I have one character scouting and triggers combat - but just for that character. I then switch to the other characters and move them (clear across the map if need be) until they're spotted and join the combat. If you're stealthy, you can even get them in backstab positions in the same turn.