To answer your question how can people be so heartless, well, my belief is that it is simply a form of "defense" on their part.  I am like you, and I feel like my sister's husband's family is my extended family, however my husband thinks I'm crazy.  His sister is the same.  The thing is, I wish I was more like them, because my letting everyone into my heart means I am heartbroken so much more.  My husband and his sister absolutely LOVE their immediate family with all their heart, and if something is wrong with them, then they feel it very very strongly, but they don't take to heart the problems of their extended family's family etc.  That way, they are protecting themselves against more and more hurt, because hurt is just a part of life.  I say I wish I was like them, because I constantly feel everyone's pain, and get seriously depressed from it.  It's just too much taking on my hurts, my husband's hurts, my kids' hurts, my parents' hurts, my in-laws' hurts, my sister's hurts, my in-law siblings' hurts, their familys' hurts etc etc.  I'm sure you get the picture.  Whereas my husband takes to heart only a dozen or so of his closest relatives.  I know it might sound heartless, but really, it is their way of protecting their heart and being able to be strong enough for their kids and spouses who need them.  Don't be too hard on them.  I'm sure they feel for their sister, they're just not emotionally tied to her grandmother.  If you're going to talk to them about it, personally I wouldn't try to force them to care about a grandmother they don't really know, but if you want to mention that their sister could do with a bit more sympathy and support, then by all means, do so, lovingly, but don't think they're monsters please.

I feel the same way with my family I was raised by my own parents so I don't know about the step and half parents and siblings. As someone has said earlier be there for your sister and support her. Tell your bro and sis how you feel about there attitude's and explain to them that they shouldn't treat her this way as she is pregnant and needs all the support she can get at this time, even if they weren't close to her grandma, she still needs there support not for the grandma but for your sister.

Cheers Queenie

Hi, 

As i see you are a great person, you do care about others, all you really have to do is supporting your sister to let her feel comfortable and to let her pass this problem, specially she's pregnent as u said, go back to your siblings and talk to them again and tell them how ur little sister needs them.

you are doing really great job, just be there for your sister and am sure she will be happy because you'll be there for her ..

you must be strong to strengthen your sister and am sure u'll honey, good luck ...