Back in the 90s I read two or three books by the same author, two set during WW1 and one set in Ireland, immediately after the war, at the time of the Black and Tans.
The WW1 books (I think they were a pair) were about girl/boy twins who were servants at a big house, and friendly with the son of the house who was about their age. The girl became a nurse, I think she may have married the son of the house at the end of the second book (or been about to). The boy worked with the horses.
The Ireland book had a cousin who had returned from the war and was slightly traumatised, and lots about the local situation from the POV of the landed gentry. There were also two girls who hadn't really been friends much before finding their own path and not just getting married.
Does anyone recognise these and know what books they were? The Ireland one is probably the more unusual!