I relate. Unfortunately, my FIL and MIL are only in a different state for half the year. I have found I just need to distance myself emotionally and stop trying to work on the relationship.
we got FIL a phone on our phone plan because he was going to rehab and we wanted him to be able to get a job when he got out. Well still no job because he claims he is going to school... well I'm not his mom, I'm not paying for his stuff so he can dick around in community college which no one lives close enough to know if he is actually going to school of not. So DF wants me to turn his phone off.
I'm sorry it's so hard when parents act like children. My fil is in recovery and it's definitely a one-day-at-a-time situation. So sorry for your frustration. You're not alone! Just gotta focus on the good.
Re: over FIL