First, how does she know the teacher is less well off? Has she computed the value of benefits, tenure, etc or is she comparing who has the higher car payment?
Second, if she gives it to the one who can make more money with it then that sibling would have more resources to take care of his siblings.
The corporate attorney may get downsized as he faces age discrimination in his 40’s or 50’s, and the teacher earning 30K now may someday retire with a 60K yearly pension. Set up education funds for all the grandkids and divide the balance equally between the two sons.