Should I take in my nieces and nephews ?

I need to vent and I also need advice please ladies. I've been with my husband for five years since then I went to nursing school and he also got a good career with the railroad. In these 5 years my sister has had 3 more kids she has 4 total and she also has 4 different baby daddies which do not help her because she barely knows the guy when she gets pregnant. She has been in our out of relationships dragging her kids from home to home because she can't get it together. Department of children has been called on her 3 times. She even smokes weed with her new boyfriend right in front of them. Well now she has been staying in motels and text me today saying she has to give her kids up because she has no where to go. I told her of course I would never let the kids go to foster care. My mom can't take them because she lives in a camper and has no means of transportation or anything. Yes my husband and I have good jobs but we also struggle time to time. Idk how I would feed so many mouths not to mention I'm pregnant with twins. Idk what to do she won't leave her low life boyfriend so she is not staying with me and she actually just text me and said the kids would be better off in foster care than living with me. What do I do ???