Hadith.477 - Al-Yasa' ibn Abdullah al-Qummi asked Imam Jafar ibn Muhammad Al-Sadiq (as) about a man praying over a funeral alone.
Imam (as) replied: "Yes, he may do so."
I then asked: "What if there are two people praying?"
The Imam said: "Yes, but one should stand behind the other, not next to him."