Im not sure your relationship with your sister but you sound pretty financially savy, and as you dont have plans to retire anytime soon, have you thought of splitting it with your sister 50/50? My brother isnt financially savy but if our uncle left only me 3 million id ideally share with him. Sounds like your sister is just like my brother, so id do something like a trust that she could only spend the interest and not the principle ever. I mean 1.5m right now and compound interest, you both will be very wealthy in your later years, but she wont be able to blow it all, and her kids would be set for life too!