Glad you took my advise. Now how would Edmund's survival change things ? For one I'd like to think that with a younger brother, and potential nephews, Henry would be less obsessed with having a son. However, if he still insists on annulling he marriage with Catherine, I have a feeling that he would oppose it. First off, it would lessen the chances of Edmund and his line inheriting the throne. Second, and more personally, he could be close to his sister-in-law and niece and hate Anne Boleyn, similar to Henry's sister Mary Tudor, Queen of France and Duchess of Suffolk. however if everything else go's OTL and nothing changes then Edmunds son or grandson (assuming he has them) would inherit the throne from Elizabeth over James of Scotland. Or hell perhaps Henry marrys Mary off to a nephew to try to keep his family loyal. Truthfully having a surviving brother for Henry changes a lot.
Pretty much this. He died young, so there are multiple, multiple ways this could go and how his personality develops. We know that Henry VII was very close to Arthur and torn up over his death, basically ignoring Henry VIII who was closer to his mother. We could see Henry VII transfer his affections for his lost son to Edmund, for instance.
His survival into adulthood makes things more interesting. Henry will probably definitely marry Catherine upon his succession, but things are more "secure" as Henry as has a "spare" so to speak in the person of his brother. Henry VIII's obsession with having a son stemmed from War of the Roses half a century before, as he feared his death and extinction of his dynasty would cause another conflict to break out. Another reason why Henry VIII went axe crazy against the de la Poles, not just because they remained Catholic, but of their Yorkist blood. Edmund being alive means Henry may see them less as a threat, but it depends on his relationship with Edmund.
As Constantine said, it's quite easy Edmund could dislike Boleyn and see her as a social climber and work in conjunction with his sister Mary to oppose the King's divorce. He would probably take a similar stance regarding his other sister Margaret's divorce attempts from the Earl of Angus.
Another interesting twist regards Edmund's marriage. Let's say Henry ends up with the same scenario, married to Catherine but his only child is married. Edmund is close to Henry VIII, and shares some of his qualities, say, his womanizing and spending habits, basically a Tudor playboy. Edmund unlike Henry, doesn't jump into marriage, figuring his older brother will do his duty and sire a son (which doesn't happen).
Henry is upset at the matter and once it becomes clear Catherine will have no more children (c. 1523/1524), Henry puts the pressure on Edmund to marry for the good of dynasty. He finds a nice European Princess or a well born English Lady (like a de la Pole... or maybe even a Ms. Anne Boleyn) and marries ASAP to sire a son for his brother, but is blows up his face (him and his wife being a bad "match" so to speak, with miscarriages and stillborns, children who die after a few days or months, ect).
Edmund ends up with his only surviving child being a daughter, and the "Great Matter" takes an Alt. Twist as Henry wants his
and his brother's marriages dissolved. It could also change things radically, say if Edmund's wife only has one difficult pregnancy that renders her sterile very on.
If his attempt to sire an heir drags on though, Catherine may actually die before it's obvious Edmund has a son with his wife (Catherine died in 1534, although I'm unsure if the conditions she was in after Henry moved her to Wales made her health worse and caused her death, or if she was not long for the world anyways). At any rate, if Catherine ends up dying while Edmund is trying to secure the dynasty, Henry can marry guilt free without breaking from Rome, and all while refusing to aid Edmund in getting a divorce much like he did with Margaret.
Another spin on the refusing to get a divorce is similar, but essentially Edmund marries earlier, does have several
living child, and say 2-3 sons, but hates his wife and wants a divorce. Henry is still with Catherine and only has Mary to show for it and is jealous of Edmund's life and his living children. Henry throws a fit as usual and refuses to aid Edmund out of fear an annulment or divorce would make his nephews and potential heirs bastards.
For added drama, you could throw in Henry lusting after his brother's wife, a pretty, younger European Princess or English gentlewoman who is much preferable to the older Catherine of Aragon. She becomes Henry's Anne Boleyn so to speak, making his "Great Matter" all the more complicated. He wants his marriage with Catherine dissolved,
and his brother's so he can marry his wife. There'd probably be an added bonus if his mistress of sorts becomes pregnant and bears him a bastard son, basically proving her "worth."
Lots of tawdry stuff, really.

But there's other more interesting things a living Edmund could effect Henry's life and reign, I'm sure.