Grieving Brother and sister-in-law who recently lost their 19 year old daughter coming to stay for 4 days

I am not proud to admit this but I am not looking forward to my brother and sister-in-law visiting from overseas soon. They lost their daughter in a tragic accident 2 months ago and are in the early stages of grieving. My thought is that I’m not going to be able to cope with their grief or I’ll say the wrong thing and upset them. I think my result from this will be that it will be a super stressful few days. My brain is not coming up with any better thoughts, I feel a bit stuck. Can you please help me clean up my thinking?