I know that from biologicall POV this scenario is borderline ASB, but still barely on non-ASB territory. Say that on 12 October 1537 Queen Jane Seymour gave birth to twins: son named Edward (more or less OTL Eddie VI) and daughter, (named Jane, after mother?) , then dies like IOTL. We are talking about person, that never existed, so I need to describe her briefly-say she's cautious, intelligent and, unlike brother, religiously indifferent. Henry VIII would surely put her in succession line above Mary and Elizabeth, who'll still be bastardised, but, untill Edward's last days, there would be no great changes compared to OTL. Edward, having full sister of unquestionable legitimacy would make her his heiress, and propably there would be strong pressure to find her proper husband. So no way for Jane Gray on the throne. Mary would find Jane legitimate, but still would claim the throne, being older. How should our 'Cautious Jane' behave in such situation?