I think they are both female. The largest one is an older female, the smaller one could also be female.
Some of my female zebra's are over 10 years old and have the exact same body and head shape as your biggest fish on the picture.
I think they are a pair, the larger one has more triangle head and the eye positions are different. he is overly plump so be careful he has not got bloat. give him diet of peas for a few days.
I would agree, larger one is male and smaller is female, judging by pectoral fins. They look really horrible fish, a bit skinny and not worth the money, send them to me and I will look after them for you.