Darkness Within

Updated cover edition found here.

At first glance, Kyle Seltzer appears to be the perfect package, the answer to a single woman’s prayers. Until Cate discovers that the deaths of his wife and twin sons have left him struggling with some disturbing and bizarre issues.
Not to worry. His identical twin brother Kane is just as dreamy, and with no notable issues.
Only after she is pregnant does Cate learn that for the past century each generation of Seltzer twins has given birth to a set of male twins. One good, one evil. One fertile, one sterile. With the exception of Kane’s great, great uncle, the twins have a habit of dying young.
And never from natural causes.