I do the opposite of some of the posters above.
First hand fold
Second hand call
In the first hand your opponent has to be worried about the possibility of you having a flush in that spot. That will make him much less likely to bluff. This factor is a key point to this hand. I don't think people are 2x pot bluffing
there often. There are people who do it, but I think a majority of the time it is going to be the flush there. There are a decent amount of heart combinations that would play this way. You may see straights and sets play this way as well. The less strong the hand the less likely your going to see it played this way.
You are really just praying for 99 or 22 for 12 combos. JT is 16 combos just by itself. Include some heart combos as well and you aren't winning enough to call.
The second hand your opponent could easily make this play with a broken draw. The price is too good to fold here. Notice the bet-check-bet line is also a common bluff line. The K on the river is actually a good card for you, because it decreases the chances of him having a king. He may assume the same for you and decide to bluff, because of that.