Since more than one family members are having the same problem, so there is a strong possibility of it being insect bit or vector dermatitis
. Even scabies
needs to be rules out.
In both of these conditions, there is development of red lesions which can occur in many people of the same family.
I would advise you to clean the beddings once and see if the development of new lesion still persist and consult a dermatologist
for proper assessment and treatment.
Hope it helps
Best wishes for a speedy recovery
Dr Geetika Paul