From what I know, children start out very open-minded about food, and then at some point, they are put off by the unfamiliar. So DS2 will happily try whatever's in front of him, but DS1 doesn't like new things, and needs some coaxing.
When this window closes, sometimes they even lose the habit of eating some of the food they used to like, if they don't get offered it for a while.
But if you keep offering foods, they may come around - last night, DS1 put his nose up at a new pasta dish, but then after a few spoonfuls decided he liked it, and ate all he was served! This was a first, and we were all very pleased.
(All this is what children tend to do. I'm not saying, "if you have a fussy eater, it's your fault because you didn't do X, Y or Z". Maybe those things didn't work for you and your child.)