Reedus has said that he fought against it, but at other times has said he'd be open to it, even said "when Daryl and Carol happen", and always talks about how amazing Carol/Melissa is, etc etc. As far as Beth he has said that " oh she's super cute, that'd be great" and also expressed irritation at people wanting Carl and Beth to get together because "they're not the same age!" He got angry one time and said the show isn't about ships, etc etc. He also gets really edgy when anyone insinuates that he isn't a 20 something.
But then, when he was on twitter and trying to win votes for something he would post lots of pictures of Daryl and Carol together, then Daryl and Beth in order to win votes.
I think the backlash from the two Daryl and Beth centric episodes really shook him. They were (and this is all not-verified info here) supposed to be his big acting moments...but people really didn't like them. Whereas Carol's main episode (the Grove) is hugely well received and critically acclaimed.
In addition, people have been trying to say "well we don't know how old Daryl is, he could be early 30s" in order to down age him into a more appropriate age bracket for Beth. But as Daryl has clear memories of Merle at juvie, that only works if you buy Merle as being early 40s and puhhhh-leaaase. 
I like Reedus, I really do. He seems kind and is a devoted father. I paid stupid money to meet him once (it ended up being canceled :( ). But he thrives on attention from fans. He is, from what I hear, extremely nice to everyone. He does seem to interact most (as in twitter messages etc) with young female fans. Not dodgily young and I'm not suggesting (nor do I believe) that he's a predator in any way. He just seems quite immature (in a Peter Pan sort of way) and likes to feel young and cool and relevant.
As far as Kirkman goes, he just has an...attitude. Like everyone last season saying Terminus would be cannibals. He practically kicked his feet and stomped and said "they're not cannibals they're NOT you have no idea what big clever idea I have!" :o When of course...well you know.
With ships he says things like "oh we are keeping Beth and Daryl ambiguous..." And then will say things about him and Carol, etc. He loves the buzz surrounding it and his show.