V.W.
My second born has the same problem in my family - even after having number 4 - still the same problem - - - It always seems she is the center - either fighting with number one - or fighting with number 3....
You HAVE to give this child extra, extra love - - - and ALONE time... It might just be 5 minutes a day - but find a time to sneak away with him to another room or the front porch - or to take an errand to the store - and let him know that's his special mommy time....
I have done this with my daughter from the beginning - she is now 12 and when I forget - she will remind me that she needs some "mommy" time....
Read books about the middle child syndrome - it can be very real..... and you need to work on it - - -
You cannot let him know the kisses bother you (even if he breathe smells bad) - - - you have to love them - you are the most important person in his life - you will give him more love - more real love than anyone else on the planet - and without that from you he will never be able to accept it from anyone else = = =