Danny and Jo are bother and sister and nothing you say can change my opinion on this. If the season finale wasn't enough proof for you than you my friend, are in a stage of deep aggressive denial.
Firstly- its not even the fact that Danny doesn't reciprocate Jo's feelings, it's the way he said he'll "never" be able to feel the same way. When Jo said to him
"I cant move on unless I know, unless I'm sure that you could never feel the same way
He didn't say anything, which in his way is a polite no. I'm not going to lie, Jo is beautiful, smart, and witty. Why wouldn't Danny think that one day he could potentially love her back the way she loves him? Its the way he implies that he's "never"going to return the feelings. You know why? Because she's his sister and he knows this. There's no way around it honestly.
Danny said "Our friendship means so much to me and I don't want to risk it turning it into something else"
And Jo countered by saying "but you can risk it for Lacey?"
When Danny told Jo he doesn't want to risk ruining their friendship and what they have together Jo immediately said "but you'll risk it for Lacey" . And Danny's response was "That's different". Well that right there is its own red flag. Just what exactly makes Lacey so different? Why risk ruining your friendship with Lacey but not Jo? What exactly does make Lacey so much different that you feel its okay to risk ruining your friendship with? You know why? Because Lacey isn't his sister and Jo is. "Lacey's different" because she isn't his family and she isn't related to him. Jo is.
When Tyler asked Jo out infront of Danny, Danny did not show any sign of jealousy or green eye'd monster at all. Jo even looked over at Danny for support or any kind of emotion regarding Tyler's boldness but nothing, just a blank stare. In fact, Danny is, or was, caption of the Joyler ship. He actually was the one pushing Jo to go out with him. If Danny really wanted Jo than how come he wasn't jealous?
Danny keeps treating Jo like a special snowflake.
"You're the most important person in the world to me"
"Our friendship is very special"
"You are the most incredible person that I've ever met"
Danny is always unleashing these protective vibes when it comes to Jo. Like he needs to make sure she's okay and safe. He treats her like an older bother protecting his little sister. Janny shippers say that Danny and Jo have this connection, I concur they do have a connection. But not the kind that Janny shippers think. The relationship m/connection between Janny is strictly platonic. The connection that Janny shippers think Danny has with Jo is actually for Dacey. Danny and Lacey are the ones with the real connection, the romantic vibes.
Danny has never once talked, flirted, or chased after Jo the way he chased after Lacey. He's never been jealous of the competition like he was at Lacey. When Jo told Danny Lacey was hanging out with Archie Danny was jealous, when Jo went out on a date with Tyler Danny was happy for her.
All Danny ever talked about was Lacey. Danny has never talked obsessively with Jo the way he talks with Lacey.
Lastly, why was Tess, Jo's mother, the only one aware of Vikram being alive? Why not his actually wife Karen or Danny, his son? Why Tess? I mean that's a bit shady dont you think? How do we know Tess and Vikram haven't been hooking up this whole time? With that being said, how do we know that Tess wasn't sleeping around with Vikram and had his baby therefore making Danny and Jo both have the same biological father?
Danny is probably aware of all of this is why he doesn't return Jo's feeling. And if this still doesn't convince you, how about when Danny shaded Jo by when Tyler asked if they were hooking up.
Tyler "are you guys... Hooking up?"
Danny "what? No she's like a sister to me".
Come on guys, don't ignore the red flags when you see them.