"Is he your son-in-law?"
Translation:Est-ce votre gendre ?
"beau-fils" is a synonym of "gendre". Report it if it's not accepted.
There is a very old synonym of "belle-fille" which is "bru". It has fallen out of use in France (don't use it!) but is still understood in Canada.
There are also synonyms of "beau-père" and "belle-mère" ("beau-dabe", "belle-dabe" and "belle-doche"), but these are argot (slang), and are also considered rude, so don't use them!
I haven't found reliable translations for "dabe" and "doche".
"dabe" seems to mean "old man"/"old woman", as in "father", "mother", "master", "boss". Calling your mother, father or boss "my old lady/man" or "the old lady/man" is usually considered rude, or at the least very informal. It doesn't seem to have the meaning of "husband", "wife" or "partner" that it does in English.
"doche" means "sorrel" (a type of plant) but I don't know if it has a secondary meaning, or is just slang, so I don't know the connection to "mother".
Typically when a noun follows "être" in a phrase like this with he or she, "c'est" is used instead of "il/elle est". Exceptions are mainly occupations, from what I've seen, e.g. "Il est médecin." Obviously, in cases with adjectives, "il/elle est" is more common, except for in blanket statements, e.g. "C'est brillant !" Hope this helps.
That's a good question. I tried "Est-ce que c'est ton gendre ?", and the supplied correct answer was Est-ce qu'il est ton gendre ?
Edited to add, later that same day: And now I'm doubly curious. The second time, I put "C'est ton gendre ?", and it worked. Why, then, wouldn't Est-ce que c'est ton gendre work? I want to understand why the longer form requires Est-ce qu'il est.
The message I have received from duolingo previously indicates that you use c'est when it's followed by a noun with an article (e.g. un, une, le, la) or a possesive (e.g. ton, sa)- so it would be "Est-ce que c'est ton gendre" or, as in your example "C'est un homme intelligent", but not when it's "Il est intelligent". This post is quite interesting/informative on this topic: https://forum.duolingo.com/comment/1957509/Use-c-est-before-nouns-with-articles-un-une-le-la-or-possessives-mon-ma
"ton gendre" worked before and should be accepted now. It could be "votre", but singular or plural was not specified.
Duo usually doesn't care about missing hyphens, punctuation, and capitalization.
In Jesuisvegan's sentence the verb "est" in the subordinate clause is missing ( and "c'est" rather than "il est" should be used):
Is it (a fact) ...
... que c'est votre gendre ?
... that he is your son-in-law?