Benjamin Croft

There is a problem with Benjamin Croft. Both Lara and Richard name him as their grandfather. Lara does so with the relic Benjamin Croft Statue Bust and Richard does so in the document A New Croft.

The tombstone marks his life from 1896 to 1970, which would mean he died at age of 74. Richard was born in 1953, so it's highly improbable that Benjamin had a child at the age of 57. So Benjamin from those years would fit as Richard's grandfather.

Or do we assume there are two Benjamins, Sr. and Jr.? Making both Lara's and Richard's claim true.