A person is unable to get up in time for Fajr Namaaz.

Answer

Most certainly the person is sinful. Never is it permissible for a person to miss Fajr because of sleep. The person should make Taubah and struggle to get up in time. If it is the husband, then he should instruct his wife to sprinkle some water on his face to wake him up. If it is the wife, then her husband should sprinkle some water on her face. This remedy of sprinkling water is the instruction of Rasulullah (Sallallahu alayhi wasallam).