Resentment doesn't understand the rational, Lookout. In quiet moments OR when he was told to do something he'd rather not have done, I'd have been surprised, knowing how destructive sibling rivalry can be, if it hadn't crossed his mind that he had to work for what he got and Sheila got it for nothing. He'd have been less than human if he hadn't.
I still don't think that there was any rivalry between brother and sister. Both were treated fairly and squarely,with or without the twins.
The ONE person whom Jeremy did express a certain amount of hostility for at the time,was Colin,who Jeremy thought would have pulled out all the stops after Sheila had had the twins,and knuckled under to support them all financially,but it didn't happen and Jeremy had to live with the idea of his sister being the breadwinner,which he openly objected to.
If Jeremy had realised how very ill Sheila was at that time,I'm sure there'd have been a set-to between him and Colin. Contrary to what others and the media say,Jeremy was very protective of his sister.