This is the 8675th most frequent Korean word.
가족들도
"가족들도" means "family members as well" or "even the family members."
In this sentence, '가족들도' (which includes '가족들', meaning 'family members', and the particle '도', meaning 'also') emphasizes that the family members were included in the group going on the trip.
가족들도 함께 여행을 갔어요.
The family members also went on a trip together.
Here, '가족들도' signifies that the mentioned family, in addition to others possibly discussed earlier, is maintaining their health.
가족들도 모두 건강을 유지하고 있어요.
All the family members are also maintaining their health.
In this sentence, '가족들도' indicates that besides other attendees, the family members were specifically invited.