Andrew & Tobias - J. I. M. Stewart - Bog

Tobias, or Toby, was fostered and then adopted as the Feltons' heir after he had miraculously survived the sinking of a ship by a U-Boat. Then, someone who is clearly Toby's twin turns up as an under-gardener. He had been fostered by a couple, now dead. There is general and disturbed confusion on everyone's part - including the boys themselves.