I JUST finished the novel and donghua for this... it's amazing! I am so excited for the drama version.... I know…
i'm keeping my hopes up since it's the same production team as the untamed and they were able to pull off the romance between wei wuxian and lan wangji pretty well even with censorship, so i hope they'll be able to do the same for tgcf ^^
How old was Lan zhan when Wei ying returned or did Wei ying grow to meet his age when Mo brought him back
i'm not sure how old were they in the drama because they changed some stuff, but in the book they meet at 15 and wei ying has been dead for 13 years, so they're at least 28. i would assume the events between their meeting and wei ying's death take place in 3 or 4 years, so they should be about 32. wei ying's soul aged with him, but i don't know exactly how old was mo xuanyu, he's no younger than 25 though, since chang clan's massacre happened (in the book) when he was 14 and that was 10 years before present time.
https://exiledrebelsscanlations.com/novels/grandmaster-of-demonic-cultivation/