Tensei Kizoku no Isekai Boukenroku: Jichou wo Shiranai Kamigami no Shito Episode 12 Discussion

After finishing the series, I have a question regarding the timeline of the series. It was said that Aaron was sealed away 300 years ago by Yuuya and his companions, including Cain's parents in his original world. Cain is 12 years old in the isekai world, 17 years old when he died in his original world, that adds up to 29 years. It is impossible for Cain's previous parents to have participated in the battle against Aaron 300 years ago as they had to have given birth to Cain 29 years ago and get isekai'd after that. That would suggest that Cain's previous parents existed 300 years ago which doesn't add up, unless I got something wrong.

@ToG25thBaam Remember how time flow differently depends on it's world? As how in Yuuya's world time flow differently than those of where Cain (Shiina Kazuya) reincarnated to.