Doctor WhoNation

 Susan

Ian Chesterton

Main aliases: Sir Ian, Knight of Jaffa, Heron

Species: Human

Place of origin: London

Main actor: William Russell

First Seen In: The Pilot Episode (non-canonical; introduction)

An Unearthly Child (introduction; joins)

Last Seen In: The Chase (leaves)

Barbara Wright/Chesterton

Main aliases: Barbara Chesterton

Species: Human

Place of origin: London

Main actor: Jacqueline Hill

First Seen In: An Unearthly Child (introduction; joins)

Last Seen In: The Chase (leaves)

 Vicki

Main aliases: Cressida, Victor

Species: Human

Place of origin: Earth

Main actor: Maureen O'Brien

First Seen In: The Rescue (introduction; joins)

Last Seen In: The Myth Makers (Leaves)

Steven Taylor

Main aliases: Steven Regret, Diomede

Species: Human

Place of origin: Earth

Main actor: Peter Purves

First Seen In: The Chase (introduction; joins)

Last Seen In: The Savages (leaves) 

Katarina

Species: Human

Place of origin: Troy

Main actor: Adrienne Hill

First Seen In: The Myth Makers (joins)

Last Seen In: The Daleks' Master Plan (dies)

 Dodo Chaplet/Dorothea Anne Chaplet

Main aliases: Dodo Dupont

Species: Human

Place of origin: England

Main actor: Jackie Lane

First Seen In: The Massacre of St Martholomew's Eve (cameo; joins)

Last Seen In: The War Machines (leaves)

 Ben Jackson

Species: Human

Place of origin: England

Main actor: Michael Craze

First Seen In: The War Machines (introduction; joins)

Last Seen In: The Faceless Ones (leaves)

 Polly Wright

Species: Human

Place of origin: London

Main actor: Anneke Wills

First Seen In: The War Machines (introduction; joins)

Last Seen In: The Faceless Ones (leaves)

 Bret Vyon

Species: Human

Place of origin: Mars Colony 16, Mars

Main actor: Nicholas Courtney

First Seen In: The Daleks' Master Plan

 Sara Kingdom

Species: Human

Main actor: Jean Marsh

First Seen In: The Daleks' Master Plan (introduction; joins and dies)