Someone who's fatherly is nurturing, protective, and gentle, the way a good father is with his child. You might be particularly fond of your older, fatherly next door neighbor.
Fatherly people have several things in common: they're kind, supportive, often older than you are, and almost always male (the female equivalent is motherly). A favorite teacher might be fatherly, or an uncle. The Old English root of fatherly is fæderlic, with similar words formed the same way in Dutch and German.