In OTL Christina of Denmark was negotiating a deal with Frederick II of Denmark to get her daughter Renata (in OTL duchess of Bavaria) married to him. The deal was interrupted by the Nordic Seven Year's War. But what if they reached a agreement before the war started and Renata left for Denmark in early 1563 to marry Frederick.
The Lorrainian claim to the Danish crown never ended up being a major issue after the death of Christina, but this would pretty much put it fully to rest. Next this means that Frederick marry a decade earlier than OTL, this would likely mean that he would get children earlier, which could means his heir could be adult when he died (Frederick will not live longer than he did, he drank and partied himself to death).
The Lorrainian claim to the Danish crown never ended up being a major issue after the death of Christina, but this would pretty much put it fully to rest. Next this means that Frederick marry a decade earlier than OTL, this would likely mean that he would get children earlier, which could means his heir could be adult when he died (Frederick will not live longer than he did, he drank and partied himself to death).