is there any relation between the clarinet and the oboe?

Nope not really. Similar fingerings, I think. I`ve never played the clarinet. I believe the bore dimensions are totally different. Also, the obvious difference that the oboe is double reed and the clarinet is single reed.

Well the general idea behind all the woodwinds is the same, so yes there is a relation. Many of the fingerings are similer.

The oboe is the clarinet`s maternal third cousin, twice removed.

Sarah,
The most important difference between the oboe and the clarinet is that the oboe has a conical bore (like the saxophone) whereas the clarinet has a cylindrical bore (like the flute). The bore is the space inside the instrument that the air moves through. A cylindrical bore stays the same width from the mouthpiece to the bell. A conical bore gets gradually wider as it moves from the mouthpice to the bell.
Consequences are:
- timbre: the clarinet is softer, the oboe richer
- fingering: the same fingering allows the oboe to jump an octave: from C to c, e.g., on the clarinet you`ll get a dodecime (C - g)

Of course, the single - double reed question is also important, but less so in my eyes. Buffet-Crampon in France experimented with single-reed oboes, and it still sounded like a (kind of) oboe, they say.

Is there any relationship between Sarah and the oboe?

Cheers


Serge