The Jewish Halacha does not require the witnesses to familiarize themselves with the couple prior to Kiddushin:
they are not required to know the couple in person before the wedding or have any relations with them
they are not required to know their names or check their IDs (keep in mind that the Ketubah (bearing the names) is NOT required for the wedding)
same for personal or family background (whether they are Arayos to each other, for example, or if they are Jewish at all)
neither they are required to [be able to] distinguish them from their twin siblings
they are not required to even see their faces, they can see them both from behind, they only need to see the transfer and hear the words!
All those conditions render the witnessing pretty much useless, as you don't even know who you witnessed, so you can never be called to testify.
If I'm wrong - please prove me wrong, if not - what's the logic of having such witnesses that have no idea who's getting married, what did the Torah want not specifying additional obligating conditions for witnesses?