<human>: I'll try and keep this short. My family is having Christmas this weekend to try and make everyone's work schedules/other plans easier. For example, my husband and I are traveling right after Xmas, and so it's a nice thing to be able to have ample time with both my side and his side. 

On Thanksgiving, my sister, who is married, showed up alone. During thanksgiving weekend, a family friend, who we'll call Man Child (MC), was invited. He and my sister spent a considerable amount of time together. I don't know any specific details, but spending time with him made my sister realize that her already rocky marriage needed to be addressed. My sister's husband is now, more or less, out of the picture; he is not living in the house. 

I've just learned that MC is living in my sister's spare room. I really haven't asked for details, because I want to respect her privacy, and I'm trying very hard not to judge her. So, I asked if MC would be attending our family gathering Saturday and she was very, very offended, but said "no." I did apologize to her for being selfish in asking her about that.

MC is pushy, arrogant, and thinks he can win others with his "charm." I have a distinct feeling he will find a way to tag along (considering he lives in the same house as her now). If he's at my parents' house, I am seriously considering dropping off my gifts and leaving. I'm feeling very much like someone has strutted into my family's life and turned it upside down, and I very much resent him for that. That's *my* issue, and I'm trying to deal with this pettyness as best I can, but I really can't see myself having a good time if he's there.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: If MC shows up Saturday (despite being told he would not), do I grit my teeth through it, or politely excuse myself and go home?