I think you've hit the nail on the head with this:

"He's still stuck at that same age ~ relying on Dad, resenting the new lady, who has usurped his place as number 1 in Dad's life, and he's constantly checking that Dad still loves him, no matter what he does, and that even the new lady can't change that."

Some of his behavior was typical teenager stuff, no doubt -- pushing limits, etc., and some of it was definitely attention-seeking.

At this point, I agree with you that "...it's a constant test, and I'm guessing that he doesn't even realise. He needs help to mature emotionally."

Part of the problem with Sonny and D.-in-Law is a sense of entitlement, and I know that drives many people of my generation (and up) absolutely nuts. S. & D.-in-L. have expressed their desire for a dresser/bureau that had been Sonny's as a child, but then say, "I see (sigh!) that you're using it in the guest bedroom, so... sigh..." I find myself astonished at such pushy, greedy, leech-like behavior, but I hear it goes on all the time.

I am trying, therefore, to keep in mind that Sonny comes from an entire generation of Americans who were spoiled rotten and had no major social issues to worry about.

Nonetheless, though, one of the big pieces of baggage that I carry around (with regard to Sonny) is the fact that he never apologized for a single thing. If he does feel guilty or ashamed about anything that happened, he's keeping it to himself, and has consistently portrayed me to his wife and friends as the classic evil stepmother!

Perhaps on some level he did feel that army life would "straighten him out" a bit; the main factor that has kept him in line for the past few years is his wife. Her bossiness, grating though it may be to some of the family, has kept Sonny on the straight and narrow, although why she supported his army decision is anyone's guess... He is out now, on a medical discharge, so he's home (permanently), not employed, and is going to medical specialists about his ankle problem (the cause for his discharge).

Hubby would agree (reluctantly) to counselling, as would I, assuming that the two of us can be crystal clear on the goals and honest about our agendas. I do think that could work...

As for Sonny, I don't know. It might be a huge, positive step if the three of us (or even just Sonny and hubby) could hash out some issues and get some clarity, and I would be willing to at least give it a try.

On a side note, here, re: "I once had a mother and baby party at my home. It was for my little-one's birthday, but it was just for mothers and babies/toddlers. My sister-in-law was invited with her toddler ~ but brother-in-law and father-in-law turned up with her ~ and stayed. They just thought that, as it was a family birthday, they could come. I had told my own family that it was not that kind of do, so they hadn't come, but ..." Isn't that a peculiar situation? lol As hostess you can't very well say, "Er, you two need to leave," but it seems unfair to your other male relatives if those two stay...

Thanks again for the advice!