I cannot tell anything from the photos; a video would allow us to observe their interaction, and this is usually the best way to tell gender, in young rams anyway, aside from actual spawning behaviour.
From your description, the ram doing the chasing is probably male. The other could be male or female, but if the male tolerates its presence close as you describe, then the smaller is likely female. However, this is not the end of the issue.
Males and females must select each other, and bond. This may occur when you place a male and female together, but often it does not. It is better to select an obvious male and female from the tank of fish in the store. Some people buy a group of rams and let a pair form, but then you have to do something with the others. Unless the group is in a very large tank, they will not get along permanently.
A pair that do not bond can spawn, perhaps several times, before the male (usually) decides he has had enough and kills the female. If they bond, they are more likely to live together peacefully, but this is not an absolute. But it does have a better chance of working long-term.
As Colin said, carefully observe their interactions. If the male seems unwilling to tolerate the second fish at all, separate them permanently. If there is acceptance, which seems to be the case here, you may luck out. Or you may not, later; I had two Bolivian Rams that spawned four times before the male turned on the female and it was over.
