Are Two People Enough to Pray in Congregation?
Question

If there are two men in a household, is this enough to pray a congregational prayer together, i.e. one Imam and one follower?
Praise be to Allah.Yes, two people are enough to pray in congregation , whether that is in the house or elsewhere. Imam Al-Bukhari (may Allah have mercy on him) said: “Chapter: Two or more form a congregation.” Then he narrated the Hadith of Malik ibn Al-Huwayrith (may Allah be pleased with him), that the Prophet (peace and blessings of Allah be upon him) said: “When the time for prayer comes, give the Adhan and Iqamah then let the oldest of you two lead you in prayer.” (Al-Bukhaari, 658)
Ibn Hajar (may Allah have mercy on him) said: “Chapter: Two or more form a congregation”: this heading was narrated in a Hadith which was narrated via various inauthentic Isnads (chains of narrators), which said that the Prophet (peace and blessings of Allah be upon him) saw a man praying by himself and said: “Will not a man perform an act of charity for him and pray with him?” So a man stood up and prayed with him, and he said: “These two are a congregation.” 
The story mentioned – apart from the words, “These two are a congregation” – was narrated by Abu Dawud and At-Tirmidhi with a different authentic Isnad. 
He (may Allah have mercy on him) also said: 
“This (the Hadith of Malik ibn Al-Huwayrith (may Allah be pleased with him)) may be understood as meaning that the smallest a congregation can be is an Imam and one follower, which is more general in meaning than saying that the follower may be a man or a boy or a woman.
The Hadith referred to by Ibn Hajar (may Allah have mercy on him) is narrated by Abu Dawud (554) who classed it as authentic. The report is as follows: It was narrated from Abu Sa`id Al-Khudri (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) saw a man praying on his own and said: “Why doesn’t a man perform an act of charity for him and pray with him?” (Classed as authentic by Al-Albani in Sahih Al-Jami`, 2652) 
It says in `Awn Al-Ma`bud: “… so that he may attain the reward of praying in congregation, so it will be as if he gave him charity.” 
It was narrated from Ubayy ibn Ka`b (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: “… for a man to pray with another man is better than his praying alone, and for a man to pray with two other men is better than his praying with one man. The more there are, the more beloved that is to Allah.” (An-Nasa’i, 843; Abu Dawud, 554; classed as authentic by Al-Albani in Sahih Al-Jami`, 2242)
However, it should be noted that what is required of men is to offer the prayers in congregation in the mosque ; it is not permissible to offer the obligatory prayers at home , whether in congregation or alone, unless one has an excuse. 
The Standing Committee was asked: If two people pray together is that a congregation or not? 
They replied: 
“If two or more people pray together, that is a congregation, but the more people there are, the better; it should also be noted that prayers in congregation should be offered in the mosque .” (Fatawa Al-Lajnah Ad-Da’imah, 7/289)
Shaykh Ibn `Uthaymin (may Allah have mercy on him) was asked about some people who prayed in congregation at home. 
He said: 
“We advise them to fear Allah and to pray in congregation with the Muslims in the mosque, because the most correct scholarly view concerning this matter is that it is obligatory to offer prayers in congregation in the mosque, unless one has an excuse. The Prophet (peace and blessings of Allah be upon him) said: “I thought of ordering that the Iqamah be given, then I would order a man to lead the people in prayer, and I would take some men carrying bundles of wood and go to people who did not attend the prayer, and burn their houses down on them.” (See Al-Bukhari, 644; Muslim, 651) 
Those people may be have been offering the prayers in congregation in their own places, but the Prophet (peace and blessings of Allah be upon him) wanted them to pray with the congregation which was performing the prayer in the manner prescribed in Shari`ah, and the congregation which Shari`ah says one should pray with is those who pray in the mosques, the mosques to which they are called when the time for prayer comes. Hence `Abdullah ibn Mas`ud (may Allah be pleased with him) said: ‘Whoever would like to meet Allah tomorrow as a Muslim, let him offer these prayers regularly where the call for them is given.’” (Fatawa Ash-Shaykh Ibn `Uthaymin, 15/19)
And Allah Knows best.