Sable could be married to Cecil's brother, Jason Colby. In the original, Sable also married the brother of her sister's husband !
Right. So Sable is Married to Jason Colby, Cecil's brother. It would make sense. Dynasty and the Colby always had those weird "family secrets, hidden children, or "son who is not the son of" storylines. So yeah, let's sum up the back story :
Dom's younger sister, Sable, dates a young Jason Colby. She gets pregnant. Dom "forces" Sable to abort (She thinks her pregnancy will shame the family, she tells her Jason is no husband material, she convinces Sable that a baby will ruin her life). Sable doesn't want to abort, but finally agrees. She regrets it everyday.
Sable & Jason relation go stronger and stronger, they get married. At their wedding, Dom meets for the first time Jason's brother : Cecil. Jason and Cecil don't have a friendly brotherhood. They never got along since they were kids. Jason has accepted to be at his brother's wedding as a duty. Anyway, Dom & Cecil fall in love. they get married, and Dom gets pregnant. Sable is really upset by the news, as Jason & her had tried many times to get pregnant, without success. Some tests will reveal that she can't have babies because of the abortion she had. It creates a huge fight between her and Dom.
As Cecil works a lot, he can't go with Dom to the doctors, to check and survey her pregnancy. Dom learns she's expecting Twins, and she's not excited by the idea. She decides to not tell to Cecil. She doesn't want to have 2 babies. So has a plan.
She decides to give one of the twins to her sister. And no-one but Jason and Sable must know. Dom fakes guilt, to explain why she's giving away one baby. She claims it breaks her heart, but she needs to fix the damages she's done to Sable. Sable buys the excuse, and she wants a baby so much that she'd agree anyway.
Sable fakes her pregnancy to her family and friends (only Jason and Dom know)
Both sister and Jason travel far from Cecil, taking a long week holidays as an excuse, while Cecil is doing business. Dom delivers secretly in a rented house with the help of Sable and Jason. She names of the babies Jeff, while Sable and Jason name the other one Miles.
Sable & Jason decide to move far away from Dom & Cecil, as they know Cecil can never meet Miles.
EDIT : if we want to twist it, (and make it more soapy) we can even have Dom a one night stand with Jason while/just before marrying Cecil. This way, the twins would actually be Jason's and not Cecil's. And this would explain while Jason would agree to raise Miles as his, because he knows it's actually his... Poor Cecil. Clueless at every step...