Upvote:2
We are dealing with the same situation. I have asked and confirmed that a son-in-law (my husband) can sponsor the hotel and flight reservations for his in-laws (my parents). You need to attach your passport copy and mention this in your in- law's covering letter as well as in a separate letter from the sponsor (you). It will help having a strong sponsoring letter mentioning why and how much you will sponsor, your bank statements, salary certificate, relationship etc. Also attach financial assets of your in-laws to reduce the look of complete dependency. Though there is no guarantee, hopefully this will help.