John and Eloise Wilson's nephew Ted's last name is said to be "Wilson." That must mean that John and George Wilson have an unnamed brother for their nephew to share their surname. Earlier in the series when their niece Georgianna is married in Season 2's "Dennis and the Wedding," George makes a point of saying he and Martha are hosting their wedding because "we're the only family she has left," despite George and John's two sisters having visited during the first season.