Very interesting thread, because it's Uganda where polygamy is a norm, and I guess, legal?
I'm sorry your S cheated on you for so long and led his gf to think he was going to divorce you and marry her and give her babies. This was pretty low of him... somehow he changed his mind and confessed to the affair? Which "truth" is he telling now, if he once led her down that garden path, while leaving you (and your shared kids) in the dark?
However, if polygamy is legal, and he could be a father to her kid(s) while she lives on a house on your land, and also available to your shared kids, this could work, if all of you were responsible and patient with sharing his time. We have a show here in the States called Sister Wives, about a family whose religion encourages polygamy (many wives with one husband) as the norm. In this show, all 3 wives lived in a huge house with their husband, and he slept with a different wife each night, and seemed to also be a present father to their many kids. It can work, if all parties want it and are respectful and good communicators. During the show the man got a 4th wife, and she had to get her own house down the street,as the main house was full. There was tension as the other wives adjusted to her and the new situation.
But! Since your h cheated for 9 mos, and also has his eyes on a couple other women, I'd proceed with greatest caution. This all sounds a bit sketchy to me. Might just be a case of testosterone overload, and the wimminfolk just have to pick up the pieces.
I've got more to say but this is already tl;dr
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
There's no lying in polyamory!
I'm a 58 year old woman with 2 partners:
miss pixi, my live-in gf, 36 (together since Jan '09)
Ginger, bf, 61, married, lives nearby (together since Jan '12)