I know I'm responding 2 weeks after you posted this but I want to say, first off, that's a nice picture of a rose-breasted grosbeak!

Secondly, although the bird's coloration is different from a northern cardinal, you can kind of tell it's in the same family because of the shape of its beak. It's got a short/tall beak with that kind of "wry grimace" look where the upper and lower parts meet. That's the resemblance that jumps out at me right away when seeing a nice, close-up picture.