Well... his ex will obviously prefer her own daughter...and I imagine that a child with a medical issue will also end up a priority too... it doesnt mean your child is less worth it but I can see how focus might go elsewhere.  Hopefully if medical issues can be resolved...things may equalize in your home...but dont hold your breath with the ec.

Wouldn’t you expect him to prioritize your child if she were in the hospital? I’m a little confused on why you expect the BM not to put her own child ahead of yours.  I think we need more information. 

I’m assuming the fact that your BF doesn’t really help with your DD is the real issue here?  It’s not SD’s fault she’s poorly & spends time in & out of the hospital, I can’t imagine the strain that takes on a parent to watch their child suffer like that. Even in intact families that child would take priority when they’re ill, their needs are greater in those moments than the healthy children.

That said, SD isn’t your child & you’re left to care for your DD on your own whilst your BF cares for his DD. I can see how that could get frustrating after a while if he’s not helping you out when his DD is out of the hospital/with her mother. I can see both sides here. 

Have you told your BF you need help, without bringing his DD’s illness into it? 

Even though he does not have custody, I can understand him wanting to go to the hospital.  Is there anyone else who can  help you out with your DD?  

I think that what you are experiencing happens even in intact families. 

A really good read is My sister's keeper. They did a movie with Cameron Diaz in it but it didn't do the book an ounce of justice. 

When you have a chroniclly ill child, the world does revolve around that child even if you have others. I have friends who are a blended family. The younger son of the husband (1st marriage) was diagnosed with cancer. He had another child and the wife had 2 from her 1st marriage. The world stopped for them for 2 years. It was all about the sick child. They tried to balance for the other kids but they failed, just like anyone in their shoes would. 

When his DD is in the hospital. DH spends time with her, even if it’s not his visitation time. Leaving you home with your DD. ??  If a child is sick you would expect the father would want to be there.  That the BM and BF would somehow will split time that someone is always there.  Just hate to say this,  This is one of the thing people don’t understand about steplife. That unfortunately when a SK is sick. Someone has to take care of it and BM and BF has a lot on contact with each other. 

For you right now, since you sound like you are alone in taking care of your own kiddo.

Oftentimes I see SM's who have children and over time observe all resources going to what is termed "the First Family", whether it be large amounts of child support that criples the second family's financiallly, or the parents of their spouses who show a huge preference for that first famiies children. Ive seen many who the grandparents will take a grand on trips and leave the other grands behind.

But heres the rub - this kiddling is sick. Thats all the information you have given as to preferential treatment, and prioritizing. I understand that you as a first time mother with her first child probably envisioned that YOU and YOUR child would be front and center, because your spouse is YOUR front and center.

But in this case, I cannot support that you and your healthy baby should take presedence over a sick child. I dont see an unbalanced situation except that you feel alone and feel like you are low on the totem pole for attention. 

Im sorry that you feel this way. One thing - are you allowed to visit this child while all this is going on? Do you have a relatinship with this child? Can you do a video chat to say hi - hope you are feeling better, lets teach the baby about its sibling...etc?