It was an old B&W horror about identical quint boys who are about 10yo. 4 of them were adopted out to good families. But at 10 they start getting terrorized and murdered. Turns out it was by the 5th baby. The grandmother comes forward and explains that #5 killed her young daughter so she threw the baby into the ocean to die.
Can you name this movie? My friend told me she has looked for the name for years!