not sure but I don't think so... since He Tian's brother refers to Jian Yi's father as Mr. Jian and to his own father as "father" so....
they're not. they don't have the same last name and like ^^ mentioned, he cheng doesn't refer to mr. jian as his father ever and addresses him in a businesslike manner always. he cheng also does talk about their own actual dad at one point and calls him 'father'. the he and jian family only have a business/gang connection. not to mention, it wouldn't make any sense for the bad guys to be only after jian yi and not he cheng & he tian if they were related..
Thank you guys ^_^
I just suddenly thought there were too many coincidences, like when He Tian went to visit his father it seemed to be an island (maybe I am wrong), and when Jian Yi dissapeared he said he woke up in an island, and He Tian's father seems someone who swaps women, and both's fathers seem to be influential shaddy people. And Jian Yi resembles his mom, so they don't need to look alike.
Then I guess He Tian's father probably works for Jian Yi's father? Cause it looks weird for such a strong person's son (strong economically, influentially and those things) to be working for other man.
By the way, why are people downvoting a question? Even if I am wrong it is just a question XD
It just struck me, are He Tian and Jian Yi actually half brothers?