Midsomer answer

[di1411]

I fell asleep tonight about ten minutes before the end - who was the murderer/s?

[jetski129]

It was the surviving brother and the one killed at the start was killed by the dead brother's son.
hope this makes sense. J

[di1411]

Thanks, jetski, though I'm not sure what motive the son had for killing the other partner (the one with the sports car).

[jetski129]

The son was in the office trying to find out how sports car and uncle were embezzling, he used the dagger to force open the filing cabinet , they struggled and uncle was stabbed in the struggle.
Son told his mum ,she told uncle who killed son!
Hope that clears that up!
J