The Lightkeepers Daughter by Jean E Pendziwol

Elizabeth, whose failing eyes have confined her to a senior home, is reflecting on her life, looking to unravel the mysteries of her family, especially that of her beautiful, enigmatic twin sister Emily. Sixteen-year-old Morgan has lived in foster care since she was a young child, bouncing from home to home, searching for one where she belongs.
When the journals belonging to Elizabeth’s late father are discovered after a tragic accident, she enlists the help of Morgan, who is completing community service at the senior home, to decipher the faded words. With a shared love of art and music, this unlikely pair are drawn deep into a world far removed – to Porphyry Island on Lake Superior, where Elizabeth’s father and his wife served as lighthouse keepers and raised their young family during the First and Second World Wars.
As a complex web of secrets unravels, Elizabeth and Morgan realize that their fates are connected to each other and to the isolated island, in this vividly written novel about the lengths people will go for love.