OK, I have a bit of info, and even though I'm in doubt, I'll share it anyway:
I did manage to find Ole Olsen and Mariane (not sure about the maiden name). I don't have any children registered to them, however, I did find out about this. Ole was born in 1850 and Mariane in 1845, Mariane in Sandur (which means 'sand' in Faroese), and Ole on the island of Skúvoy. They married in 1870 (I don't know the date), their marriage was tragically short, since on April 30th, 1870, Ole was lost at sea. Mariane herself died 11 years later on August 18th, 1881.
Although they share the surname, Eva is not Ole's sister, since she's from Sandur. It is possible, that Mariane's maiden name was Olsen aswell, and in this case, it's possible that Eva and Mariane were sisters, but I can't prove this atm.
I hope this helps a bit. I can look deeper into it, if you'd like.