The original, 2004 Hellboy opened with the birth of Hellboy and his discovery and adoption by Professor Broom.
The relationship between Hellboy and Professor Broom is central to who Hellboy is, and what side he fights for.
Based on Ian McShane’s comments to Fandom, it sounds like this reboot will go back further, and perhaps show more of the origins of Professor Broom and the B.P.R.D. It also sounds like Hellboy and Professor Broom will be butting heads quite a bit, as Hellboy struggles with who he is.
Hellboy is very much a story about nature versus nurture and destiny versus agency.