We made sure people were vaccinated with DD#1 (particularly my dad as we assumed he'd be around her a lot).
Unfortunately, DH's parents aren't very pro-doctor (long story but neither of them are very health-conscious and DH was never taken to a dentist growing up and only saw a doctor for when he was sick, no normal checkups.) So I am assuming neither of them are vaccinated, but on the bright side, they both work at small companies and aren't around children (like DH is. He's vaccinated.) They're also total homebodies. So hopefully their risk of exposure is limited since they don't get near other people very much. Still, I will be vigilant to look for signs they might have it and if I suspect DD#2 has been exposed, I won't hesitate to get her treatment.