Of course. But that is a different usage from the family sense.

Regardless, if a French baby is adopted by German parents, the family is still a German family, while the baby is genetically French. The same applies to genetic classification of languages: adopting/borrowing words does not change the genetic classification even though the etymology of the words is non-native.

Grouping languages into families is based on grammatical similarities. Why is vocabulary, word etymology, adstratum, etc. not included with language classification?

Created new thread.