Lawman
Without trying to lose the spirit of Christmas, or taking the matter out of proportion, the reading of your post suggests that this was not a passing visit for a few minutes but indeed a much longer term "visit".
There is a clear distinction between going into First Class and speaking to someone briefly, and staying there for an extended time, which your posts suggests was the case.
Whilst I think everyone will have a view on what a "few minutes" constitutes as against a longer visit, I doubt any on board staff would take exception to someone going into First Classif it were done briefly, and did not become a prolonged visit.
Personally I think there is a point at which you "family" stepped over the mark, and many on here take that view. I think the bigger issue here could well lie with the possible failure of the TM to protect the First Class, which is something I notice Virgin are very bad at, indeed currently I am in correspondence with Virgin about that very issue. I also believe that the placing of the TMs "office" in C was a decision that could only have been made by someone without a brain. The best position would be to the centre of the train against the First Class, so that not only can the TM keep an eye on First Class but is also in a more central position in the train.
I know that there are people who will try it on in First Class by sitting there until thrown out, and I have to say that Virgin are appalling at protecting their First Class against say the former GNER. On the basis that passengers travelling First Class have paid substantially more than those travelling Standard but irregularly occupying First Class seats I feel Virgin are giving their First Class passengers - who incidentally do subsidise all these cheap fares - a raw deal. Hence my correspondence with them.
On the basis that your family did occupy First Class for more than a short period, I think there are a number of issues that you need to consider, many of which are already made, that have fundamentally changed the relationship from a blind eye being turned to a more formal condition.
...Firstly, i again like to reitterate that it was a few people that came through, (Mid Journey) to speak with us in First Class from Standard, since the carriage was empty, they sat down to chat and were offered refreshments. Also there were children involved.
The number of people who came "through" is completely irrelevant, as is the fact that there were children involved. What on earth does THAT have to do with anything, other than they may now have gained the impression that it is permissible to ignore the difference between Standard and First Class if and when it suits them.
...If they had been asked to return to Standard Class they would have done so with no issues.. so no... the crew member would not have been a bad member of staff if he had asked them to do so... ....
Quite irelevant that they would have returned "with no issues". The point quite simply is that they were not authorised to be in First Class. In the event of an accident they would be judged to outside the terms of their tickets, and this would certainly have repercussions on their legal ability to claim damages.
By extension of the argument so far, it becomes the case that it is permissible for anyone to wander into First Class as long as they are happy to return to Standard "with no issues" ?
....Secondly.. they were not "sneaked" into 1st Class, they just came through to chat! (there was humour in my first post)....
Ah that makes it OK then I guess. Maybe I shall propound that argument next time I travel ?

Note the humour on my reply
......Thirdly, i take offence for my family and i to be accused of "criminals" or trying to fair evade as this was not the intention....
Your family have committed a number of acts which the legal system specifies are Criminal in nature. That entitles people on here to quite correctly call you "criminals". Taking free refreshments constitutes "Obtaining Goods and Services by Deception" as the
free refreshments are not free but are included as part of the First Class ticket price, are it is clearly specified that they are only provided for passengers holding First Class tickets. That is one reason why First Class tickets are so expensive.
...I had commented on this thread by "monkey" to again agree with him of the service we received on our journey as the crew member could have been strict with his rules and moved them back..
The On Board catering staff member is not trained in revenue duties and therefore it is not within hois job to check for the eligibility of passengers to be in First unless asked by the TM.
I am not suggesting that this happens on all the time, nor am i boasting about it, and I wouldnt expect it to happen again, however we were provided with an excellent service by this crew member and are grateful that we had a chance to all sit together unexpectedly! (for a while)!!
I think the comment "excellent service" flows from the fact that those who were not entitled to, were suitably fed and watered for free.
....I am rather bemused that this has got such a reaction... I know everyone has an opinion and in mine, i dont think its a big deal.. merely just an act of good will!!
There was NO act of "goodwill" because your family members were not accorded anything special. They irregularly entered and sat in First Class for an extended period when they had not paid to travel First Class. They then proceeded to consume food and drink to which they were not entitled, and which was only provided on the belief of the on board catering staff that those benefitting from them were entitled to do so. I have previously seen on board catering staff request sight of First Class tickets before giving refreshments when the train has been especially full and Standard Class passengers have gone and sat in First Class and not yet been challenged by the TM. I have also seen and heard amusing scenes where the TM has told someone that whilst they would have been turfed out without charge, the fact that they have consumed food has altered the situation, pointing out that ticket they hold is not valid and they will have to purchase a full single First Class ticket at a cost of £140.
Finally
Lawman suggests much. I do rather hope you are not a Policeman or other form of law enforcement officer.