Well, there's no reason why he can't purchase it from a conventional real estate transaction standpoint. But, it depends on a couple of things.
1. Who has rights to the property? Do the siblings and he have decision making power over the property together?
2. Can your husband qualify to purchase the house from a financing standpoint?
3. Is your husband prepared to take on the responsibilities of owning a house?
These are all questions that need to be answered before a comprehensive determination can be made. I would consult a real estate attorney to know exactly what his/your rights are.
Good luck, Jayjeemarie!!!