I'm stuck between making a long post with lots of backstory or doing a drip feed - I've changed some details for anonymity.
My father and I have a difficult adult relationship, he raised me alone with no help from my mum who I haven't seen since I was a young teen. He was a good father all things considered and tried his best. I think he has undiagnosed mental health problems which have worsened with time. He thinks that I am transferring anger to him because of what my mum did. He thinks that raising me gives him cart blanche to be part of my life. He is so angry now he has started 'grey rock'ing me - so I don't know where he lives or who he spends time with. If I ask him what he's been up to he'll say 'not much' and refuse to elaborate. It's the bones of relationship at all now, and I'd probably not speak to him at all if it wasn't for wanting him and my kids to know each other.
He wants to visit them for Christmas, and currently lives in the foreign country of his origin. He has family there but doesn't speak to them, lots of burned bridges etc.
Because he raised me alone, our relationship was very intense. He has strong religious beliefs that I no longer hold and this infiltrates everything. He also tends to latch on to conspiracy theories and to have paranoia. Worries about online banking etc. He hasn't worked in years and complains about the cost of living all of the time. He says he wants to 'come home' but has no property here, so he means my home, with my DH and kids.
He wanted to come for 8 weeks at Christmas, but I can't cope with him in the house for that long, and I'm worried he might never leave. He has a lovely relationship with his grandkids, but I find him so so difficult. I've offered for him to come for 3 weeks max. Even this I will struggle with and we will almost certainly argue at some point. He finds this boundary very offensive, his beliefs mean that he thinks that families should not have boundaries and that I'm ungrateful and disrespectful. He is mostly outwardly kind but occasionally angry and says mean things which I find hard to forgive. He thinks that being passionate is part of his culture, but I'm very British and find this rude.
AIBU? Hard to know if having boundaries with close family is healthy or cruel, given that my upbringing was unusual I can't get a proper read on it.