If your boyfriend's grandmother is dying, he may be struggling to accept it. Having identified that your boyfriend is having a hard time is an important step. Each of us experience anticipatory grief in our own ways and knowing how a loved one is hurting can be as difficult as knowing what to do to help him. Help your boyfriend through this difficult time by focusing on a few simple themes in your interactions.
Listen to what your boyfriend is saying. Pay attention not only to his words but his body language and energy. Provide a safe environment where he is able to openly speak about what he is feeling or experiencing. You don't always have to say a lot in return; your responses can be nonverbal. In listening, be careful not to force him to talk about what he is experiencing. It may be natural for you to get together with your girlfriends to talk about what is going on as a way of dealing with it, but this may well not be his style. Understand that reactions can be quite different for different people.
Find ways to support him. Take the initiative to take care of the things that he is not able to focus on right now without taking over for what he can and wants to do. Small gestures in his life may not generate a comment back from him but they can make a real difference. Depending on how he is being affected by his grandmother's dying, many areas of your relationship may slip through the cracks. This is not the time to assess the state of your relationship, though. Instead, realize that among all the ways you support him, the greatest is simply being there. At times this will be awkward for you -- for instance, if you didn't know his grandmother -- but having you at his side is tremendously supportive.
Silence can be golden. He may need some space to be able to process what is going on. Grandsons often have a hard time crying in front of people, including people close to them, so he may need some space just to cry. Consider that both support and allowing space can be delicate, but it is very important to find the balance. As you give him space, watch out for signs of depression. If he starts to isolate and show other depressive symptoms, try and work out if this is normal for him or something to be concerned about. If he starts sounding suicidal, seek professional help.
As you interact with your boyfriend while trying to help him through this difficult time, don't be fake with your responses. It is important to be responsive to him while being authentic. It is OK if you and he have different reactions to similar situations. Each person's response to grief is different and this response will vary from one situation to another. Being genuine and sensitive with him will give him the safe space that he needs to process the emotions he is dealing with as he works through the grief of losing a significant relationship in his life.