Science fiction games don't normally use the rules for familiars - these magical companions are typically only seen in fantasy campaigns. Because of the magical link with their spellcasting master, familiars share part of their senses with them. When it comes to fatal damage, the death of a familiar usually causes some serious shock to the system of the master. By symmetry, if the master dies, the familiar feels a great shock, but seeing as how they are usually small animals with a fraction of the hit points, this is usually fatal to the familiar.

Stretching the rules to familiars with more body mass and muscle than the master may lead to some minor incongruities.

[Reminder: Our guest commentators have not seen Rogue One. Part of the fun is seeing how their untainted impressions re-interpret the movie through the lens of our comic.]

Transcript

Bria: Quick! We have to get Chirrut to Polish Mustard in the next three rounds!
GM: Baze lumbers towards Chirrut, mowing down troopers in a mindless fury of destruction.
GM: The troopers recoil in fear, but there are dozens still shooting.
[SFX]: Dakka! Dakka! Dakka!
GM: Baze reaches Chirrut and cradles his dying master.
[SFX]: Pow! Pow!
GM: Pete, do you want to roleplay a dramatic final conversation? Before Baze dies of a broken familiar link?
{beat}
Chirrut: Nah, I'm good. {dies}