Are sea otters related to weasels?

My second grade students asked this question, so we looked it up. According to Wikipedia , weasels and otters are related. They belong to the Musteliedae family, along with badgers, sea otters, wolverines, ferrets, martens, and mink. This is a difficult family to classify scientifically and some of the animals have been classified as being in this family through the use of DNA. Animals in this family are carnivorous and tend to have short legs and anal scent glands. Skunks were thought to be part of this family, but DNA evidence has shown that they are actually not in this family. This family is commonly called the Weasel family.

However, no cases have ever been found of otters and other mustelids producing young, even through means of artificial insemination. Factually speaking, the only factor that keeps otters in the family Mustelidae is their similar appearance to weasels and, in particular, minks, as the DNA of otters and weasels is incompatible. So, in a sense, no, otters are not related to weasels, except by taxonomical classification.