Katie is not over the breakup yet, even though it's been about 5 months. She buried her feelings and is just now starting to dig them out again. Jared and I have grown very close recently. About a month ago, Katie told Jared that she thought he and I were going to get together, and she was upset about it. Jared told me this even though Katie didn't want me to know. It hurt my feelings that she would tell this to someone else instead of me when it is a direct criticism of my behavior.
Since then, Jared and I have gotten even closer. We always drive around together (there's not much else to do in my tiny little town), and I'm developing feelings for him. I've noticed a few changes in his behavior as well, but I'm not sure what they mean. He intentionally makes physical contact more often, and I catch him glancing at me when he thinks I'm not looking. He also replies really quickly when we text or snapchat, and we have nice conversations about passions, dreams, and memories. But he doesn't act as comfortable with me when Katie or other friends are around. I'm not sure how to figure out what he's feeling.
Katie is still in the process of getting over him, but she's making really good progress. She doesn't talk about it with me because she feels uncomfortable since I'm such good friends with him. I don't know if I should tell her about my feelings for him or if I should wait until I have a better idea of what Jared is feeling.
The situation seems to be very clear. Apparently by what you say, Jared is also developing feelings for you, but might thing that he will hurt Katie if he acts all natural with you when she's around.
I wouldn't overthink it.
Regarding Katie, the broke up long enough before you two starting seeing each other as something else than friends. There's no guilt in what you or Jared are doing.
I wouldn't shove the relationship on Katie's face, but she will have to get used to the idea of you two being together.
I hope this helps.
You definitely should feel some guilt though, that is natural. Seeing as you are going to knowingly hurt your friend quite a bit to make yourself happier.
Also, be prepared to lose Katie as a friend, because I think that is a strong possibility if you go ahead.
However if you want to be with him you have 3 options
1) speaking with her about it on your own and maybe hurt her that way before you act
2) keeping it from her,act first and then let her find out
3) act to see if you even do get together and then let her know afterwards
I think each of those options have their merits
I personally don't favor option 2- but to each his or her own