As others say it is a phase. If dp can relax and not get upset it will pass quickly enough.
My dd is 14 and we have been through several phases, including a very rough patch. Becoming a lot more relaxed about it often helps.
At times though my wife has not appreciated my 'relaxed' approach. When dd was 3 or 4 she came down just after midnight to find us cuddled up singing to Aristocats scoffing popcorn and drinking milk.
I think for me one of the hardest times in our relationship was when she was 9 and decided she was too old to be read to in bed. I had gone through the early stages, 'red, blue, ball, red ball, blue ball etc to being asked to read the same story over and over again. We finally got to a real good book and was half way through it when she decided she was too old. I often joke dw came up to find us fighting over the book. I pointed out that it had got to a good part and I wanted to see what happened next. She told me to grow up and walked off.
hmmm come to think of it she used to say that a lot to me dd still laughs because I insist bedtime reading is a cruel hoax by children to put their dads in their place when they are older. Secretly I still miss it though, but don't let on.
But seriously, I doubt if your son has gone off his dad. The relationship goes through stages and I often find when my dd breaks off one phase there is an adjustment period and it picks up again. With us now I cannot get into her music, so that is a mummy thing, but mum cannot get into her tv shows so that is a daddy thing. Though if anyone has any understanding what Naruto is about I would appreciate a quick run down
I say it a lot, but if parents can relax and go with the flow it does help to get past these phases much quicker and easier.