Serial monogamy creates a new kind of relative, the "ex-". The "ex-wife", for example, can remain an active part of her "ex-husband's" life, as they may be tied together by legally or informally mandated economic support, which can last for years, including by alimony, child support, and joint custody. Bob Simpson, the British social anthropologist, notes that it creates an "extended family" by tying together a number of households, including mobile children. He says that Britons may have ex‑wives or ex‑brothers‑in‑law, but not an "ex‑child". According to him, these "unclear families" do not fit the mold of the monogamous nuclear family.