NZ - imagine being the step mum of your poor little boy and how hard it would be for the poor step mum - are you for real?
The vast majority of SPs will make sure any child that is not healthy had those issues are not welcome in the other household and contact is quickly lost with the NRP.
As a mother who has a sick child, and who has spent immeasurable time in hospital - believe me the parent who is there is invariably the mother, who is invariably single. Sick children put a strain on relationships that you can not comprehend unless you have been there. If the NRP visits - fellow parents in the same position stare in amazement.
If the NRP visits you can pretty well guarantee the new wife, DP will phone, text and generally interfere in the little time the NRP has with their child.
Post hospital the NRP, usually finds an excuse not to have their DC in the house - which usually stinks of the sodding new DP/wife not wanting to cope with the DC.
This is not a one off, go to any support group for sick kids and you will hear this scenario 80% of the time.
My recent trip to hospital, EX turned up on day of surgery, was supposed to stay in the hospital second night so I got a break - come 2300, I get a call, the evil new DP is struggling and he has to go home. Bollockless twat for falling for her crap and evil evil selfish bitch for doing it. ( times 6 and counting)
Being an SM is challenging but so are an awful lot of family scenarios.