My Family Has Been Sick With The Flu And Everyone

my family has been sick with the flu and everyone keeps getting sick over and over times 3 with runny nose , cough and body aches nausea . My two sons in their 20's and healthy people keep getting it they get better like no fever or aches but the cough remains since thanksgiving and never stopped just gets better for a while. Then over the holidays many relatives got sick after being together in one house and my two sisters who have been healthy got pneumonia they are aged 64 and 68. Could my sons be carriers or have a mild case of pneumonia and are passing it around?