What do you do if in-laws don't save for retirement?

Hello all,
I have a bit of an issue. I have been dating my bf for 2 yrs and we would like to get married soon. One HUGE reservation I have is that they have no retirement, no savings, and still have ~20 yrs left on their mortgage. I am scared to marry my bf because I fear they will become leeches. They are in their 50s, no pension and rely on government medical ins. If the dad gets hurt and can't work, they're screwed. My bf and I are 23 and graduated with degrees in engineering and science, respectively. We planed for our future in order to be able to support a family. His parents, however, did not pursue an education or lucrative trade, got married young, and decided to pop out 10 kids. Dad makes $40,000/yr, mom is SAH. They say they "rely on the Lord" for everything… A little too much if you ask me. They take a passive approach when we talk about their savings and again "rely on God". I am scared because I do not want their lack of income to hurt my and my future husband's savings/kids college funds/inheritance/ect.
I bring this up with my bf and he says not to worry and that if worse come to worse, his siblings will help out (6 are daughter who are uneducated, married, and don't work, 4 are boys-bf and one of his brothers are only ones who aspired to anything). So, what do you think of this situation? Do you think the sister's husbands will be willing to help pay the parent's mortgage and expenses? Or does it seem that the financial burden will inevitably fall on my bf

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