Dear MAX,
I think in the episode where Kramer ran away and Jerry was
frantically trying to find him he called up Kramer's mom Babs and ( as he
did <not> then know the name Cosmo) he asked if she knew where her son
"Kramer" was ,he then specified "your middle son"! So ,Kramer is one of
at least three sons ( possibly five or seven) ! No names or situations
have arisen with them,though! Walk Proud and Far,
Leon.