Let's see.
Hayate-Almost always alone, and did everything by himself as a child. Had some parasitic parents that sucked him dry. Got Abandoned when he was no more use.
Nagi-Dead parents since childhood. Klaus and Himegami was there, and eventually Maria came.
Hina-Got abandoned since childhood. Had a great sister who was always there for her. Was adoped later by loving parents.
Maria-Got abandoned since birth. Was adopted. Mikado seems to be very fond of her. Living with Nagi eventually.
Ayumu--ehhh? Nothing happened.
Athena-Dead parents since childhood. Cursed by God and was trapped alone. Always in solitude. Did everything by herself as a child to climb up from level 1.
Tragic childhood rating.
Ayumu<Maria<Hina<Nagi<Hayate<Athena