Edmund's difficult birth led to his mother's addiction to morphine. Since Edmund is very close to his mother, this is hard for him. He has traveled extensively but has come home ill. He is diagnosed with consumption and may not survive. He loves his brother, Jamie, but cannot always understand him. He is aware of his father's failings, but can also be sympathetic toward Tyrone in a way Jamie is not.
Jamie is deeply unhappy. He has a poor relationship with his father and is devastated by his mother's failure to beat her addiction. Jamie works as little as possible and prefers to spend his time drinking or visiting the brothel. He has a deeply complicated relationship with his brother, whom he both loves and resents.
Tyrone is Irish. He had a difficult and impoverished childhood but became a somewhat successful actor. He gave up the opportunity to become a truly great actor when he took on easy roles to make money. Tyrone loves his wife deeply and is seriously hurt by her continued drug addiction. He loves his sons but gets angry at both of them often.
Mary was an Irish convent girl when she met and fell in love with Tyrone at age 18. She loves her husband very much, but their marriage has not turned out as she expected. She spent a lot of time traveling with him while he performed, and she feels the lack of a real "home" very strongly. Her second son died when he was quite young, and her third birth (Edmund's) was very difficult. The doctor gave her morphine to help her recover, but she became an addict.