Nothing odd about that in Denmark, although it is not very usual, but since the seventies some children have called their parents and aunts and uncles by their given names.
I think a lot of DILs and SIL use their parents-in-laws given name in preference to addressing them as "svigermor" = MIL and "svigerfar" = FIL, which formerly was the done thing here, at least until the young couple had children, when most grandparents were addressed as such, even by their own children and children-in-law.
What does sound odd to me is hearing a son- or daughter-in-law addressing parents-in-law by their given names whils his or her spouse still addresses their parents as mum and dad, or the equivalent.