This is complicated, clearly, as you can tell by the title. My brother (I'll call him Sam) turns 30 early next year and this is a big deal that he's survived to it. He's an undiagnosed autistic with other mental stuff and is consistently in a psych ward every couple of years. As a reward for making it to 30 and to give him something to look forward to, we're going to do a trip together and he's given the okay to open the invitation to anyone else in our family and maybe some of his friends. Here's where it gets tricky. Sam and I(33F) grew up in different households halfway through my his life, and my dad essentially saved me from a really abusive situation (out of one and into another). When my dad tried to get Sam, my mother manipulated him into never wanting to leave her (among other things). This was on top of visits going from once a month to holidays only because I wanted nothing to do with her (Sam knows none of this). I say all this to say, Sam and my dad have a strained relationship. To him, our dad abandoned him and my dad's behavior has only enforced that. Our dad hasn't seen my brother in almost 12 years (since the day he stopped paying child support) and it hurts my brother so deeply. Their relationship is just sending memes at this point. There was a short stint where our dad wanted to go on vacation together, I said let's include Sam, and after three days, we got into a big argument and after I said he needed to do more effort into his relationship with Sam first, our dad essentially threw a tantrum and it ended all talks of a vacation. I have tried to dissuade Sam from wanting a relationship with this man (I stopped talking to our dad for seven years, partly due to how he treats Sam, partly due to my own issues with him). But idk, it's such a missing piece for him. It's not even a distance thing, because our dad will take trips to see his friends and other family. So the wbita part: I want to (secretly) invite my dad to this trip. Secretly in case he bails. But I also don't trust him to actually come, so I want to guilt him into it essentially. Just kind of let him know what a jerk he is to his only son and how unloved he has made Sam feel over these years and how he needs to step up and do this one thing before either one of them dies (I'm tempted to reach out to dad's gf to see if she's willing to help but I've never spoken with her before). I don't know that it would get the desired effect but I don't particularly care about my own relationship with this man so I'm willing to risk it. He doesn't even have to stay, he can just show up for a few hours. But he owes Sam at least this one thing, and then maybe it would stop haunting him (or maybe it will make it worse, I really don't know). I know I might be overstepping on their relationship too but our dad listens to me more than Sam and Sam won't stick up for himself. So WIBTA if I laid into our in an effort to force him to show up and see my brother?