Conversation so far:
Does Cosmo Kramer have any parents? Who are the parents?
Kramer was estranged for a long period from his mom, Babs Kramer. His dad never makes an appearance.
What about Cosmo Kramer's dad?
Kramer mentions that he is the last male member of his family, implying that his father had died.
Did Cosmo Kramer have any siblings?
Was there any other family member mentioned?
He also mentions in that he has or had a deaf cousin, from whom he learned fluent American Sign Language.
How was relations between Cosmo Kramer and the deaf cousin?
How was Cosmo Kramer's relation with his mom?
Kramer was estranged for a long period from his mom, Babs Kramer, who works as a restroom matron at an upscale restaurant.
How was Cosmo Kramer's childhood?
Kramer said that he ran away from home at age seventeen.

Question: Any other notable events from childhood?
Self-contained rewrite: Any other notable events from childhood for Cosmo Kramer besides running away from home at age seventeen?