It is not a /v/, but English natives (and sometimes others) often have difficulty distuigishing the difference. The Dutch /w/ is different from the English one, and is closer to but not the same as the /v/.
Here's some more info on the sound: https://en.wikipedia.org/wiki/Labiodental_approximant
De kinderen van wie. The children of whom.
But that would make for an odd sentences though.
After some rearanging, you might get this sentence, which is acceptable.
Van wie zijn deze kinderen
Wiens kinderen zijn dit
To whom do these children belong
Whose children are they.
Who knows what Belgians will use ;) sometimes it feels like a completely different language (most of the time actually, just one that you can sort of follow).
So while there is no synonym for wiens (because it is a personal pronoun like mine) the sentence I gave is an alternative correct way to say it in official StandardDutch
(However I can clearly hear someone say wiens in a Belgian accent so I'm pretty sure I ve heard someone from belgium use wiens. Perhaps it was the presenter of legomasters which I watched a month or 2 ago. I could be wrong though)