Well, there are multiple cases of women carrying a mummified fetus (stone baby) for multiple years (I think the longest I've heard was 60 years or so). The first time I read about it years ago, I remember some articles and videos were titled "Woman pregnant for __ years".
He's been friend for 15 years but never curious to ask about his friend's exorcist job untill now? And the sister who knew that her brother expertise in supernatural never come to consult with him first? Well that the mystery in its own I guess?