I was talking about this recently in my weekly French class; my teacher is a French national and she and her partner came over to England about 10 years ago and settled in East Anglia, running a very successful cafe with delicious home-made food and welcoming fires, all very much in the French tradition and very popular too! I can drop in for a cup of coffee and a croissant before heading upstairs for some serious French conversation. She tells me that the French too have no words for this complex interweaving of family ties but simply have the same name for in-laws and step-relations. Thus my daughter-in-law, my step-daughter and step-daughter-in-law-to-be are all my belles filles, my beautiful daughters, and my step-sons etc are my beaux fils. So they are all my beautiful children!
And it was wonderful to see so many of them over Christmas.