Well, so far the family is structured thus, as I see it:
1) Rolth is the father and necromancer. His goals are to return his undead wife to life, teach his son his trade, and revenge himself on a world which he believes unnecessarily hates undead.
2) the 9 year old son, Raven, who adores his father, wants to be a necromancer too, but hates his "younger brother" and blames him for his mother's death. He both loves and hates his mother, because he needs her, but he feels abandoned by her. He is far more evil than his vengeful but ultimately inward-focused father; he could easily become a serial killer.
3) BIAJ, aka Mrs. Necromancer. She wants to return to life, but is unaware that her younger son is actually both a ghost and a construct, but in neither case is he alive and waiting for her. If she knew her "baby" was gone and no longer needed her, she MIGHT be willing to move on. She was evil, but mostly in a self-indulgent way. Now, she's half-crazed with boredom, confinement and loneliness.
4) younger son, now an infant ghost in the house, but also a construct built in the last year or so who resides in the basement. Note that these are two totally separate beings, and neither is tied to or aware of or interested in the other... (except that since neither is aware of the other, one might be angered by the existence of the other). Neither of these entities is evil; the baby is merely terrified and alone. If it were given a chance to pass on in the company of a spirit who could guide it to the proper resting place, it would go happily. The construct has no spirit; it should either be destroyed, bound to some form of control, or awakened in some way so it could gain a spirit.
I don't see, at this point, any real way to cause the baby spirit, for example, to "go to" the BIAJ. Nor for Rolth to be made aware that his wife is exhausted and going insane in her confinement.