Family members that could be heavily impacted by the relationship would be their children and the victim's parents.
The children witnessing this dysfunctional dynamic may grew up thinking that how their parents where is normal and will expect similar outcomes in their relationships, continuing the cycle. Plus if the batterer is attacking the partner when they get upset imagine if the partner isn't there so the batterer may take out their aggression on the kids. The victim's parents may feel useful in this situation because their not able to fully protect their child from what is happening and may be unaware of all that has a occurred.
The suggestion I have for the prevention of inmate partner violence would be to continually speak out, let others know what is happening to you. Abuse only continues to thrive in silence, speaking out can help decrease the fear one has in leaving the
batterer.