user -there is not universal hatred of second wives and step mums, circumstances dictate alot of views but such a blanket statement is wrong.
OW/OM - I think you would be inhuman, not to struggle with dealing with that person. However long the relationship lasts. Usually the new couple run off to utopia the kids get treated appalingly by the departing parent. OW/OM do not want a reminder of the past - if it lasts ( odds are stacked!) then 10yrs down the line if it survives, the injured party still has to suck up the insult every day and agree isn't lovely that it has all settled down! Come on most of us have feelings!
Never ever will SM be Mum, second mum , SF be Dad or second Dad - sorry line drawn.
Second wives after split and nice to step kids - no issue. Do not stop contact, make it difficult and treat kids as equals - utopia. It does exist but is hard work on all sides - seen it and admire those that manage it.
Bitch SMs like Notjuliaroberts to name one on here - complete contempt. Their dcs are better, behaved, eat better, wash better, smell better, play better, nicer, do not want SCs in the house dread them coming hide away, do not take on holiday, organise holidays so they are not included, resent monies being spent on them, no space etc
Those who muddle along and get it right some of the time and mess up occasionally - no problem. Sometimes we all need to take a step back and see the bigger picture.
Interestingly - I have gone from 1 and 3 - in the same person - relationship failed. To in the last 6 months Ex has a new girlfriend - who is lovely - combination of 2 and 4 - kids happier. That is all that matters!