A Christmas Threesome-OPP

Today's OPP has nothing to do with the three wise men. A woman is hosting Christmas dinner at her house and one of her guests wants to bring more than one significant other.

Mike & Kate-
I need advice because I have no idea how to handle my holiday situation. I'm hosting Christmas dinner at my house and my entire family is coming over. There should be about 20 adults and who knows how many kids. My older brother got divorced this year. He has 2 kids from his marriage of 20 years. These teens will also be coming to dinner.
The reason I need advice is because my brother is bringing not just one woman to dinner but two. He is in a threesome relationship. Both these women are in their 20s. Now I honestly don't care what my brother does as he goes through this mid life crisis but I don't think it needs to be brought to my Christmas dinner table.
I tried talking to him about this to see if wouldn't bring the girls to dinner. He said they are all in love and he wants to spend Christmas with the women he loves. I then asked he could then just play them off as friends and he said absolutely not. If he wants to kiss one or both and hold hands with both then he should be able to. Plus he said he going to ask them for an official commitment after dinner by giving both women a ring.
My concern is that there will be young kids in the house, my 90 year old Grandmother will be there, my parents, etc. Non of these people have any idea that my brother is in a threesome. Why does he need to do this at my house? He claims this is a moment he wants to share with his entire family so we can them embrace these women. He doesn't want to hide his relationship. But does Christmas really have to be the place to do this? He says if he was proposing to one woman then no one would have a problem with a Christmas proposal. I don't want to tell him not to come. He's my brother and I love him. But this is too much to explain to my 7 and 9 year olds. Am I being to uptight about this? How would you handle it?

Appreciate the help and Merry Christmas!

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