it is the unvaccinated four-year old family member who is at risk. assuming your well-immunized boys are well they pose no risk of any vaccine-preventable diseases to the unvaccinated child but wait until this little guy starts pre-school or kindergarten. he will most definitely be exposed and be at risk.
is it safe for my boys 2 and 7 safe to be around a 4 year family member that has never been vaccinated? scared<negative_smiley>