Quite strong as symbolically predating the same plot as covered in a literal manner in We Need to Talk About Kevin, about the soul-searching and emotional fallout of being a parent to a mass murderer, by 37 years. Both films lack a solid murderous reasoning-- not just derived from social-environmental factors, nor just a mutation-- and contain the belief of everlasting parental love and responsibility for your kin.
Unfortunately, this was the least popular of the movies I showed in Art School. They liked the more typical stuff like 'Satyricon'. I think any good film education has to have stuff like this. Satyricon is easy to appreciate, because it's like a moving painting. 'It's Alive' is an allegory about loving your children despite them being monsters.