Familiar from birth with a specified custom, behaviour, accoutrement etc.; naturally suited to (it).
1977, Gāmini Salgādo, The Elizabethan Underworld, Folio Society 2006, p. 16:
This [...] involved not only wearing certain clothes as if to the manner born, but being familiar with the gestures and the style of conversation associated with such clothes.
2008, Jeremy Alexander, The Guardian, 10 Nov 2008:
Stephen Ward, a winger converted to emergency left-back two months ago, now looks to the manner born.
Etymology
From Shakespeare, Hamlet, Act 1, scene 4: "But to my mind, though I am native here / And to the manner born, it is a custom / More honour'd in the breach than the observance."