Actually, Kion does take a lot after his grampa, and I see where people are coming from when they point that out.
First thing that catches my eyes is his nose, as it is brown and more square then his dad's, like Mufasa's. Kion's tuft of mane looks brighter then Simba's, too. When you compare Simba and Mufasa, you might notice Mufasa looks slightly more gaunt, square and stronger then his son, and when you compare cub Simba with cub Kion you could say the same. The shape of Kion's eyes resemble Mufasa's more then Simba's too, as they appear a little more round. Kion also has bushier eyebrows that go all the way down until the pale part under his eyes, which is also larger then Simba's. He also appears more muscular then his dad was when he was a cub, possesing broad shoulders and larger jaw, just as Mufasa looks stronger then adult Simba, even in TLK2. While Kion's fur is probably much paler then Mufasa's, you can also say that both Kion and his gramps have smaller contrast between their main pelt and muzzle/paws/... then Simba.
Then again, all this is hard to point at due to all the design changes Mufasa and Simba got it TLG - Mufasa lacks his brown nose, pale nose patch, lightly scruffy mane... so to put all this I mainly looked at original TLK Simba and Mufasa for reference.