Not the right build for 100% cavalier, and a very heavy head; but for his size, could well be a cocker/cavalier cross (cockalier) which are one of the more common mixes. There are B&T cockers and ears etc look far more cocker to me. It's always very hard to tell as you can mix two quite different dogs and have the offspring look mostly like one side. I have pics here of puppies from a rescue cavalier I took in that you'd think were labs!! They look exactly like labs -- the only thing cavalier about them is they are reddish rather than gold. I also once saw a dog that looked exactly like a cavalier with very short legs -- must have been a dachshund or corgi cross but you'd have thought it was a cavalier except for the telltale legs! I'd say your handsome fellow is definitely part cocker, if not a small cocker (you can get dogs well short of and over breed standards as we know with cavaiers!). I'd doubt he is cavalier mixed with something else -- besides very possibly being a cockalier that is. You might try googling for pics of cockaliers for comparison and see what you think?