Family got gi bug a week ago. no one had fever. all our symptoms had subsided for 4 days. but now, 1yr old has fever 9 days later since start and 5 yr old vomited again. all after we all felt better. is this reoccurrence abnormal or concerning ?

Many viruses that can cause these symptoms,as well as food poisoning. Likely that the children have a different illness than what you all had last week.So,no this is not uncommon or concerning.Treat symptomatically,with fever reducers as needed and fluids.Be sure to let your 5 year old's stomach rest and wait a couple of hours from vomiting;start with small amount of fluid, increase slowly.