Okay, first book had the story of two brothers (twins?), one of which was born without legs. The boy without legs goes outside at night and is possessed by some spirit and proceeds to torment his brother.

Second book is about a family that moves into a house that has a glass floor which allows them to see water gushing into darkness which I believe has something to do with a water wheel. There is a cemetery nearby and there is some local lore about leaving offerings to appease some entity who takes one of the kids.

Thanks in advance.