Hey Dixie-girl
Well - the boys are twins - but very much two separate little fellas - as with any siblings, they can be night and day - but of course having 2 the exact same age, in the same house.... and a baby bro too... well - it's easier to see the differences and wonder about how "unalike" they are.
Could he be just wanting to be different to his brother? He has his own personality and characteristics and I know you are allowing him to grow in his own skin - he may feel his need to argue a point because he does feel a little less secure - but all you can do is allow him to come to you as and when he wants to hug you - and when he argues back - question his argument in a constructive way. So much easier to say that a? when they are backchatting to a certain degree. Know-it-all kids - well they all "know far better than their folks" - HA
The kids also have had different friends, different peer groups - this all has an effect too - they have different ailments and different understandings of their individual roles in the house.
PaPaDixie is away a lot - so your little fella, even tho he is used to it, may be reacting to that in a way - when MaMa is the head of the house when PaPa is away - certainly he may take on a role there. That's also a time where is can start pushing his boundaries - which is what kids will do as they get older. I know he's only 8 and not in any way like my kids - but both mine reacted differently to their Dad travelling. Maybe your little fella is trying to be the "man about the house" - wanting to be the one who is right, in charge and therefore butts heads with you.
I think, from who I know you to be - and just my opinion - that you are doing a fine job with him - and you are an excellent Mom - you need to keep encouraging him to understand he can be different from his brother and quiet and doesn't need to know-it-all quite yet and if he wants one on one time with you - tho I understand how impossible that may be - that he can have that when you can do it.
If he is less creative than his brother, a straight A student and quiet - he maybe thinks more or on a different level than his twin - so encouraging him to express himself in a less "knowing" manner could be a start - just keep encouraging him with positive reinforcement and not lock heads with him - he's too young at the moment to be "rational" but he also has to know his boundaries.
He's beginning to find his feet and he's stepping out in a new direction.
He's a kid - from an early age they do believe they "know" everything. We just have to show that them we know stuff too without engaging them in battle.
(you know my history.... so whaddo I know - but just my opinion a?)