As the director of Yerma, I would try to focus the audience's sympathy on Yerma because Juan and her sisters are talking about her while she is out getting water from the fountain and also Juan is being very patronising towards her while she isn't there.
"Where's she gone? One of you ought to have gone out with her. That's what you're here for." Juan, Pg 181.
He is also being patronising to his sisters as well as Yerma. I think that Juan would deliver this line in a very cold matter and will be standing up with his sisters sitting down at a table while drinking some wine and the sisters will agree with him not to aggravate him so they won't be kicked out of the house.
"A man has his job to do" Juan, Pg 181.
When Juan says that to Yerma he is saying that women don't have jobs like men and should stay in the house and not see the light of day, but with his sisters keeping 'guard' on her will not be able to get out anyway.
Yerma's response to Juan would be a little bitter but in a nice way is pleading her point to Juan.
Again, in this scene the question about children crops up a Juan tries to get out of the situation but Yerma persistently talks about it for him to give reply.
"The same old story, eh? It's five years now, isn't it. I'd almost got over it." Juan, Pg 182.
Yerma says to Juan that he has his sheep, pruning leaves and markets to keep him occupied but Yerma should have children to keep her busy, but there is none take care of and Juan's response is to one of her brother's kids.