The big thing about Gabriel Belmont is that he becomes Count Dracula in Lords of Shadow 2. The Lords of Shadow games give every impression that they have nothing to do with the other Castlevania's. That being said, I don't actually believe that to be true. The Lords of Shadow games could easily be in the original Castlevania timeline. If certain liberties are taken.
It's worth mentioning also that despite being a "reboot", Gabriel Belmont's family tree does connect to Trevor, Simon and Victor Belmont. Proving that they do infact, connect.
See also: Lords of Shadow Family Tree
For the traditional timeline clan, see Belmont Clan.
The Belmont Clan was founded by Gabriel Belmont, a knight who belonged to an order called the Brotherhood of Light. He was raised by the order after he was left at their doorstep when he was an infant. Gabriel took the surname of Belmont, after his love of mountains and the high places of the World.
See also: Lords of Shadow Timeline
1047 - Gabriel Belmont (Castlevania: Lords of Shadow)
Marie Belmont
1073 - Trevor Belmont (Castlevania: Lords of Shadow - Mirror of Fate)
Sypha Belmont
1101 - Simon Belmont (Castlevania: Lords of Shadow - Mirror of Fate)
Selena Belmont
2057 - Victor Belmont (Castlevania: Lords of Shadow 2)