The Shadowrun system is OK, but I'd prefer to take advantage of the game's existing synergy rules:
If a player has 5 ranks of Knowledge(nobility), they get a +2 synergy bonus to their Knowledge(Dwarves) check (or vice versa, if you'd prefer) when learning something about Dwarven nobility.
Now you say, "but there IS no Knowledge (Dwarves) skill!" Add it. Make a Knowledge skill for each race, where that skill covers everything (nobility, history, culture, anatomy) having to do with that race. It's the racial analog of Knowledge (Local).
(Make it an automatic class skill for that race, too. So all Elves can learn Knowledge (Elf), even if they don't go Wizard or Bard. This causes problems with classes like the Loremaster since it now becomes easy to get two Knowledge skills as class skills, so be careful.)
So, you can now do synergy. Maybe call it a +1 synergy bonus for every 2 ranks of "related" Knowledge skill.