Fever can support the immune system's attempt to gain advantage over infectious agents, such as viruses and bacteria, and it makes the body less favorable as a host for replicating viruses and bacteria, which are temperature sensitive. Infectious agents are not the only causes of fever, however.
Your sister's grandson is your great nephew. You are his great aunt (if you are a woman) or his great uncle (if you are a man).
Legally your kids and your sisterâs kids are first cousins but at the DNA level they are half siblings. They share twice as much DNA as run of the mill first cousins! What I thought Iâd do for the rest of the answer is go into a bit more detail about why you and your sisterâs kids share 25% of their DNA.