Wikipedia has a great article on name suffixes spelling out, for instance, when it’s appropriate to formally use the terms “Senior” and “Junior” with respect to family members who share the same name. A boy who is named after his grandfather, uncle, or cousin should (strictly speaking) gain the suffix “II” (or “III”, etc) whereas a boy named after his father would be “junior”. I never knew that distinction - I thought that “junior” and “II” were synonymous!

