A general rule that I follow for Demon's Souls & Dark Souls is: if you can't beat a boss (or bring his life close to zero) after 3 attempts, STOP. You'll only frustrate yourself and hate the game if you continue.
You need to leave the boss alone for a while and upgrade your armor/weapons, upgrade your vitality/endurance, or build a different type of weapon to use against him.
As far as the 4 kings are concerned:
1) If you're not dodging their sword attacks, you're doing it wrong. Build endurance and increase stamina regen - Havel's Ring, Dark Wood Grain Ring, Cloranthy Ring, etc.
2) If you don't have some way of blocking the magic attacks, you need to find a shield or armor with high magic resistance - Crest Shield, Elite Knight Set, etc
3) Summon help - In your first playthrough, Witch Beatrice has always served as a suitable distraction (this is pointless for NG+ & beyond)
4) You need high damage/high speed weapons to kill off the kings quickly before more spawn. I like fire or lightning versions of the Gargoyle's Halberd, Scythe, Scitmitar, or Iaito.