hmmm, Who of u remeber the first enemy we saw in Kakashi Gaiden? Well i kinda noticed that The enemy and Deidara look alike.(couldnt find a good pic cuz Inane's scanlation were more MQ than HQ)
Maybe they could be father and son...
Although they do look similar we cant say that he is deidera's father untill Kishimoto brings up deidera's last name or shows some-kind of contection btw the two characters. If it was just based on looks then we could have said that Lee is gai's son (XD). Which as we all know is wrong.
Also the Iwa nin didnt have any special hands. How could deidera get those hands?
As Ayah stated earlier he could have gotten it from his mother(like Haku).
Heres where the connection btw the two characters seems broken.
Alright we know that the Iwa guy died at the hands of the forth. Now wouldnt Iwa's partners know that he was killed by the forth or by fire-nins? Wouldnt they tell his family how he died at the hands the fire-nins(or the forth)? And wouldn't his son seek revenge against konohagure nins? When deidera fights kakashi there are no signs of personal hatred btw Deidera and kakashi. He doesnt show any signs of hatred towards the konoha-nins. Hence I dought he is the son of the Iwa nin that was killed by the forth.
The purpose of the at charcater was only to portray the awesome might of the forth's shunshin no jutsu and also to show Kakashi's first attempt with chidori on an enemy. Thats all, there is no hidden story to the death of the Iwa-nin. Atleast according to me.