Foolish Mortals by Jennifer Johnston

All families are complicated, but some are more complicated than others. And Christmas can only make matters worse.
After Ciara's estranged father is nearly killed by his second wife in a car accident - or was it an accident? - Ciara begins, gingerly, to reenter his life. As her troubled family gather for the holidays, is it too much to hope that they begin to find peace at last? Of course it is.
With cross-dressing twins, new loves and an unpredicatably monstrous matriarch, Christmas was never going to be easy. But it proves both more disastrous and happier than any of them could have guessed.