A sister clade is one of two haplogroups or subclades that are at the same level on a phylogenetic tree. For Y-chromosome research, this is sometimes a brother clade. For example, on the maternal tree [..]

One member of a pair of clades originating when a single lineage splits into two. Sister clades thus share an exclusive common ancestry and are mutually most closely related to one another in terms of [..]

A term used to describe clades that are on the same level of a haplogroup or phylogenetic tree. For example, R1b1c1, R1b1c2, R1b1c3, etc. would be considered sister clades.