No matter, whose children, in a relationship, they SHOULD always come first.
They didn't ask for the divorce/separation, but they lost in it.
So, when Mum/Dad, finds a new relationship, the kids must be a big part of it, and their emotional needs must come first.

I disagree. No-one should come first nor last in any healthy, balanced, mature relationship. Division of attention and division of care is fluid and is not set in stone - and is a sign that a person knows at what time said attention is appropriate and to whom or what it should be designated at that particular moment. There is no first nor last - other than a populist stereotypical notion. And that is where the problem lies.

To state to anyone - male or female, adult or child - from the outset that they will come second to something or to someone is not acceptable, and could be deemed quite off-putting and impractical to those who put no-one second to anything/anyone and who also know what constitutes a balanced, sensible, mature and respectful relationship.

The same applies to the term 'you will always come first' - this instils time-bomb complications, which arise when the individual perceives they have not come first, and who then starts to cause trouble as a consequence. It also instils selfishness, self-centredness and demanding, which is quite childish and offensive when carried into adulthood.

The use of the terms 'should' and 'always' are completely unreasonable expectations, and set one up to fail - as is clear by reading about what has been going on in this thread.

Flexibility is the key in relationships, with no set first nor last. Then there is harmony and acceptance, rather than demands and inflexibility - we leave the latter aspects for the kiddies who know no other way until they grow through acceptance and patience, as opposed to demands and rigidity.

And for those of you who've quickly skim-read through all of the above, and are now just reading this bit before clicking the 'back' button - if you read all of the above backwards as well as forwards - over and over, there is a prize mentioned within it... called: happiness!

Children should always be put 1st. Regardless of if their urs or ur partners. Its the children who suffer when things go wrong and they usually blame themselves when parents break up. If ur partner has kids u have to put them 1st and treat them right or they can cause a break up cause the parent will put them 1st over any new person their life. But a lot of the younger generation dont care about their kids as much as the older generation. They put their happiness before the kids. As a result the kids go out get drunk and cause trouble to get attention from their parents.