I would say, YES, in any later marriages, where kids from former relationships are involved, it is usually the case (and in fact, usually a good thing) for the parent to put the kids first, always. Part of this is borne out of the parent's sense of guilt over the divorce---the need to forever make up for the family break up. And, as you well know, your kids are always your kids, though spouses can come and go.
You may find it helpful to re construe a bit, what you want in terms of a spouse who is a soul mate. You can have a husband who puts his kids first, with your blessing, but who is utterly reliant on the marital relationship to keep functioning everyday, face stress
, be a parent, "schlog" on at work when you are tired, deal with conflicts and problems. A couple can still be the source of energy and emotional support 100%, despite the fact that each of them will set the relationship aside for a time to help their kids out, be a mom or dad. So what I'm getting at is that being soul mates is NOT incongruent with putting your kids first, because the roles you fulfill in each area are so different. Also, as kids get older, they have less and less need for their parents to help them, be dependent on their parents, etc., as they have their own life, their own kids etc. So this childcare and support issue is in part, a life phase that will probably change over the years.
I hope this information is helpful to you. Let me know if I have overlooked any aspect of your original question. Please hit the green Accept button at the bottom of this screen. Thanks.