My guess is that most people overthink the story. Sigrid has had miscarriage once and is desperate to have baby. When Henrik is born she comes possessive and overprotective about the child. She just loses her mind and tries to protect the child from everything. She didn't show any emotion when giving her son away after being so obsessed over the child before. Isn't that odd if the child is her own? Other baby is stolen I think. Ultra did prove that there is no twins and cloning is quite far fetched.
Review of El Hijo
