I Think that Tom Branson is a Brilliant Father and is doing a Great job as a single Dad and the late Lady Sibble is looking down with a great smile on her face and willing him to do the right thing
And then Mary continued to spend one hour a day everyday with the children, like the Dowager Countess before her, and they all lived happily ever after…….
I'm not sure if it still was in the 1920s, but for a lot of English history it was technically illegal to marry your late sibling's husband or wife. I don't think either of them would have considered the other as a potential match.