I read this article some of its factual and some not:
1) As children Bertie and Edward were close although its true that Edward was favored as the eldest and the heir. In fact, until Bertie and David went to school it was the three oldest children (including Mary) that were particularly close. I think the taunting was more of what an older brother does to a younger brother. From what I read, Mary ruled the both of them.
2) Elizabeth (the Duchess of York) was actually quite fond of David until Wallis Simpson made an appearance. She and Bertie certainly weren't in the same social circle (more homebodies than club people) but the Yorks did socialize with Edward when he was with Thelma. I think Elizabeth (and a lot of other people) felt that Wallis separated Edward from Bertie but I think some of that had to do with divergent interests (at this point David was/had become) very close George, Duke of Kent. Also, why you (Wallis) want to socialize with someone (The Duchess of York) who disapproves of you? I wouldnt And really, Bertie was happy with his family life. But of course, there were a lot of other things, you should check out the Queen Mother's relationship with the Duchess of Windsor to see specific examples of the two personalities of the women clash.
I've read that Elizabeth had been friendly with Edward for awhile - there were even rumors that she wanted to be with him, not Bertie (rumors that I don't buy at all). I have Shawcrosses' biography of the Queen Mother and her letters indicate there was a great deal of friendly affection between her and Edward (even if they didn't hang out together due to lack of common interests). I don't think any one person can separate siblings - maybe Wallis had something to do with it, but if so, it was Edward's choice. If he had wanted a relationship with Bertie and even his other siblings, he would have maintained one.......but he didn't.
3) There was some talk of bypassing Bertie but they was quickly passed over. Plus the DoK had a questionable past with some of his romances and drug history.
4) I don't believe David made fun of Bertie when they were young. He certainly did mock up as they matured; paticularly once Wallis came on the scene. Since David felt that he was done wrong by his family (in regards to Wallis HRH's title) he basically demeaned them all.
David basically shut himself off from his entire family, not even just Bertie, and I find that sad. I find him to be, the more I read about him, not just selfish, but cruel and callous.
5) George V was a demanding and non emotional father this is true --- he made sure Bertie wore braces to correct his knock knees; made him write right handed when Bertie was a natural left hander.
I really symapthize with the Windsor children - poor Bertie had the worst of it, with his physical ailments, didn't he? It's clear that George V loved his children (based on some of his letters to them), but I'm not sure what he hoped to gain by treating his children like he did. I guess he thought he was doing right by them in that they would grow up to be dutiful and disciplined, but he ended up damaging them.
6) Its interesting to note that Bertie didn't stammer until an event happened in his life. I want to say Edward VII died (it could have been sooner). Bertie was very close with his grandfather, who is reported to have considered Bertie his favorite grandson.
I thought that he started stammering around 7 or 8 based on general overall treatment by his father. I do think Bradford's biography may have mentioned that the stammering started after Bertie and the rest were reunited with their parents after a long trip. They'd stayed with their loving grandparents for months and clearly it wasn't easy going back to living with George V.
7) A lot of info reported after the Abdication is true: Edward was not welcomed back to England...there was some concern he was scheming behind the scenes. He might have thought he could act as Regent for Princess Elizabeth, but Queen Elizabeth the Queen Mother wouldnt' have let that happen. Even if she didn't want Mountbatten to take control. And actually, at this point, the Duke of Kent is dead...and the Abdication pretty much changed the path of the career of the Duke of Gloucester (Harry another brother) who was now tied to England in case he needed to act as Regent for Princess Elizabeth. Plus Edward was not truthful when negotiating his financial settlement.
From what I've read, Bertie felt as if having his brother in England would be like a medieval king having a rival claimant on the throne - and I can't blame him. Here he'd be trying to do his job and at the same time his brother would be pandering to the public, trying to win their affection and undermine him at the same time. The fact that Edward lied about his finances, continually harrassed his brother while he was trying to settle in as King - really, he was a royal pain in the behind. As I've read about George VI's illnesses, it's really quite heartbreaking. I get the idea that he could really only do his job intermittently - but I'm glad they never named a regent. What a tragedy to be that sick and incapacitated at such a young age.
Really, the introduction of Wallis and the Abdication truly changed and damaged the relationship between the brothers.
Like I said, some of its factual (based on the books I have read The Relucatant King by Sarah Bradford) but a lot of it poetic license by the author.