This test may have already been done on your grandson. Many nurses and pediatricians in birth centers and at clinics automatically test for developmental dysplasia of the hip (DDH). It wouldn't hurt to ask if it has been done.
A family history of DDH is a risk factor for this condition. Girls are at greater risk than boys, but boys can have DDH. In fact, these two known risk factors (gender and history) aren't really good predictors. Only about one out of every 75 babies with a dislocated hip actually have either of these risk factors.
But early detection is helpful in watching the condition. Many times the child develops just fine and doesn't need any treatment. But for those who end up with an unstable hip, early intervention can help prevent surgery later.
The medical record should indicate the results of this test. Perhaps you could suggest your daughter call and ask if the test was done and what the results were. If the test was not conducted, then it can be done at the next well-baby check-up. Encourage your daughter to take the new baby to all of these early appointments.