]I did find it ironic, however, that he chose to bring Jo back into his life just as his situation could be most hurtful to June.

I disagree on the timing. When June became engaged, she was never at home anymore -- she was out and about with Bosinney or other social engagements. Old Jolyon felt her absence severely and he knew he would get worse once she was married and in her own establishment. When Old Jo was feeling most vulnerable due to his age and in need of company, his greatest source of comfort was moving on. He understandably went looking for his son. At the time, he had no idea that the engagement would hit a snag and that June would need him. I don't think that it would have been fair for Old Jo to abandon Young Jo and his family again because June's circumstances changed. Instead, he chooses to include both of them. June is still going to inherit a good sum of money and she is invited to live with them with the offer that he'll set her up in her own establishment if it doesn't work out.

It is true that June seems selfless when she asks her Grandad to buy Robin Hill, but I believe that she is still in love with Bosinney and she wants to help him. Recall that she goes to his rooms after the trial with the hope of getting him back. (We should talk about that chapter in a different post because it's such a good scene between Irene and June.) I also believe that people have the potential to very naturally act in two different extremes when they love someone and it's over -- you either lash back and seek revenge or take comfort in their pain, or you continue to do selfless things because you love(d) them so much and don't wish them ill, even if it's over.

Lastly, recall that there are several references in the book about June always seeking to help the underdog. For example, when she goes abroad with her Grandad, she befriends a woman who is dying of consumption and she tries to will her back to health, unsuccessfully.