This article is about becoming a mother, it helps us understand Izzy's deep connection to her baby even though she may not be a conventionally fit parent.
https://www.psychologytoday.com/us/blog/in-flux/201404/becoming-mother
This scholarly article examines the effects of losing a child on a marriage. It shows that losing a child is in many ways more intense than losing another family member.
Here is another article about marriage when losing a child. It is a little lighter read and includes information about dealing with the tragedy. https://www.aamft.org/iMIS15/AAMFT/Content/consumer_updates/grieving_the_loss_of_a_child.aspx
Here is a PDF about death within families. Though it is rather long, it can help us decipher the nuances of everyone involved with Danny's death.