Here is some info on HCV
A few pages in your question is addressed
http://www.hcvadvocate.org/hepatitis/factsheets_pdf/Newly%20Diagnosed_10.pdf
Sorry to hear of your cousin’s recent diagnosis. Thanks for taking a moment to check in and find out about this disease, too by the way.
Hep C (HCV) isn’t transmitted over environmental surfaces or household exposure; so any vigilance only need be restricted to blood. In fact, it’s really only transmitted via blood-to-blood contact; its only rarely passed via sexual intercourse, for instance.
Most of us got this either from IV drug use or receiving transfusions or blood products prior to 1992.
Your cousin should be able to hug, kiss, share eating utensils, and pretty much anything with the kids; he/she should be careful with medical sharps, sharing personal care items like clippers, toothbrushes, stuff like that.
Good luck- maybe have your cousin stick they’re neck in here to say hi—
--Bill
Your grandchildren are at no risk at all. The only thing that could cause transmission between cousins is if the infected cousin bled into an open wound of one of the other kids. Most of us here lived for many years, even decades, before hepatitis C was found and our families and friends are all fine. Just urge the children to tell an adult if they hurt themselves and see blood. An adult should cover the wounds of an infected child.