I have long been puzzled by our BM, who has NO hobbies or interests, does not clean, cook, garden, grocery shop, do laundry, etc, left the child care to DH (he got up in the night), etc. She works a f/t job, that is it. She also treats her kids (21 and 17) like friends, with a total inability to parent.

Well, I like to understand human nature and I came across something called "dependent personality disorder, the immature subtype"

"Immature Dependent

As a variant on the pure pattern of dependent personality, the immature dependent has a permanently childlike view of the world, along with underdeveloped life skills to match. This type of dependent is extremely inexperienced and unsophisticated. For some patients, this stems from a lack of energy, while others are too easygoing and never develop any ambition.

A large percent of these patients find the responsibilities associated with adulthood, including assuming a fixed gender identity, frightening. Immature dependents often seem irresponsible and even neglectful to their immediate family members."

My DH is a caretaker type so at first he didn't mind so much doing almost everything (ex: away 2 weeks and comes home to dishes not done once) There were other factors (personal) why he gave in to her marriage demands but he tried to be a good H to her. Once the kids were born, she did even less. It was almost like role reversal, where she worked (although he did too) and came home late while DH did the suppers and baths and bedtimes. BM also did not exercise and gained massive amounts of weight.

When they got to be teens and SD (bi-polar I think) raged against her dad's limits and got in trouble, etc. BM caved and sided with the kids every time, undermining DH. So it became 3 against 1, with DH doing everything while they all snuck around and smoked and partied and in BM's case, cheated. He lost his job and that made him less valuable to BM, also.
When he tried to change it, BM divorced him, figuring that slave DH would still support her, do everything around the house, while she got to screw around and party. Big buzzer! And of course, him meeting me started the whole 'victim' thing.

Main point of this, DH and I were talking the other night and we had some major insights. BM has shifted her "authority figure" fixation to the kids. But not only does she try to please them by letting them do what they want (sleep-overs with revolving door boys for SD and out on the town partying for SS despite DUI and drug arrests) she is also putting them in the parental role with attendant responsibility. SD does all the cleaning and SS has to do all the home repairs and maintenance. SD has complained that there is no food in the house so she goes shopping.
I think it is vital for kids to do chores but not ALL of them. The house is a disaster, the garage and cellar always look like a drunk strewed garbage around. At times, when SS has gotten sick, DH has had to TELL BM to take him to the doctor. She is also in a financial mess despite selling property for an extra $48K over the past two years. She put a deck on although the roof leaked, that kind of thing. Always new junk in the house while the good stuff disappears or gets broken.

We have wanted SS (17) to live with us since BM freely admits she "can't control" him. He has said he wants to move, called us crying about it, but in the final push comes to shove, he won't come, saying he "can't leave Mom." I think that she is so dependent on them that she guilt-trips SS into staying. DH doesn't want to force him but with all his trouble lately, he did tell BM that he will take her to court and get him placed with us if he gets arrested again. He has been arrested for pot, DUI, and underage drinking twice, and had truancy charges against him. Obviously it's not good for him to live with Mom. There are no consequences, direction or limits on either SK.

Actually, these insights made me feel more compassion. I pray that BM meets someone soon that she can transfer her dependency to so those kids can be set free. It's a very sick, frustrating situation and poor DH is torn between yanking SS and letting him learn the hard way, as he seems to be doing.