This HaBO comes from Gayle, who wants to find this historical romance:
Long time reader, infrequent poster!
I read this book possibly early/mid 2010s. It was probably a Regency. In the prologue, a couple is about to be wed. He had a title and she was marrying above her station. His best friend was a woman on the estate next door and everyone thought they would get married instead, but the hero and heroine fell in love. After the ceremony, the heroine went to find her new husband and saw what she thought was him and the other woman locked in a passionate embrace. She runs away.
Chapter 1 is almost 7 years later and no one has heard from the heroine. Everyone is encouraging hero to have her declared dead so he can re-marry and get an heir. The childhood best friend is now a widow and wants him.
They are at the theater or opera when the door to the box opens and it is his wife. The reason she came back was because she had an almost 7 year old son, whose birth was witnessed and had been documented as his heir.
Can this be solved?
If she ran away following the ceremony and had a son shortly after, that must mean… *waggles eyebrows*