Teen SS regressing

[Magda72]

Hi all - this is not specifically a step issue but am hopeful some of you might have some experience/knowledge of this.
Dp's eldest is just turning 18 with one more year left in school. Dp & I live together with his three (dss1, dss2, 15 & dss3, 12) visiting us eow, holidays etc. or dp having them in a house he has kept in the town where they live with their mum. Dp very hands on & does all school meetings, dentist appointments etc. All kids (inc. my 2 at home) get on fine - it's not the Brady Bunch but it's good.
Dp & I together 31/2 years, dp & exw divorced 6 years.
Dp said at the weekend that he's a bit concerned about ds1. He's a smart kid & gets on well in school & has himself well organized with school/study etc. but when he's with dp, dp finds him clueless. I'd observed this myself but never said anything. He'll forget to lock doors, has NO sense of direction, can't find his way anywhere, can't figure out simple stuff like operating the shower & even forgets to tie his shoelaces - all normal teen stuff but not aged 18.
His two younger brothers would buy & sell him & yet he's quite mean to them - eating treats they've bought for themselves & the like. Basically his behaviour is really childish & quite out of whack with his age.
Dp doesn't think he's on the spectrum. His brother has dyspraxia so dp doesn't think it's that & besides he's very coordinated when he wants to be.
He doesn't have a great relationship with his mum & it seems to me that when in dp's company he sort of regresses back to wanting to be minded as it's almost like he knows dp can take care of him.
Has anyone had any similar experience with this sort of behaviour?
Dp torn between thinking there's something amiss & thinking he's just lazy.
Also, teachers have said he mixes in school but he won't do anything with his friends outside of school hours.
Any thoughts?

[TempusEejit]

I don't have that much experience but I would guess your key observation is "it's almost like he knows dp can take care of him."

When DH and I were going through some issues with DSD we bought the book "Get out of my life...but first take me and Alex into town" which we found incredibly helpful. One of the sections is called "giving too much" which explains how adolescence is a time of increasing separation between parent and child and parents who do too much for their children may ultimately get in the way of that process. I also had good advice from my counsellor who explained how easy it is as parents to go from supporting the child to supporting the problem. Does your DP bail out his DS if he gets lost/can't work the shower etc? Could he show him love and attention in some other way such as a shared interest?