In a hospital who can visit a coma patient?

Probably unlikely unless the family explicitly grants that person permission (probably by filling out some legally-binding visitation list for the hospital).

A friend of a sister will not make the cut to see her unless he can prove he is her long lost twin brother who was adopted at birth…

Or he could sneak past the overworked, overly tired nurse who is dozing off at her desk.

Is she pregnant by him?

Most hospitals will let anybody visit.

A friend of mine was in the ICU in a coma 3 weeks ago. A coworker of mine (and his) was able to go in and see him.

@Rarebear a policy that always seems sensible right up until exwife, current wife, 2 mistresses and mother turn up to visit at the same time (this was a a situation my mentor left me to deal with while I was a student)