His father does not pray unless he prays with him – should he pray at home for his sake?
Question

                I m wondering about something, my father does not pray regularly, usually when he prays its because i tell him to come pray with me, my question is firstly, when i go pray in the masjid for example, or pray alone, then i see my dad can i pray a second time with him (e.g Isha twice?) And also is it better for me to make the prayers with my father or in the masjid.
Praise be to Allah.Firstly: 
Praying in congregation in 
    the mosque is obligatory for men who are able to do it according to the more 
    correct of the two scholarly opinions, as has previously been stated in the 
    answer to questions no. 120 and 
    8918. 
Based on that, it is not 
    permissible to stay away from praying in the mosque in order to pray with 
    your father. 
But if you pray in the 
    mosque and go back home, it is permissible for you to pray with your father, 
    and it will be a naafil prayer for you, because there is a reason which 
    makes it permissible for you to pray in congregation again. It is proven in
    al-Saheehayn that Mu’aadh (may Allaah be pleased with him) used to 
    pray ‘Isha’ with the Prophet  (peace and blessings of Allaah be upon 
    him) then he would go and lead his people in prayer. Narrated by al-Bukhaari 
    (701) and Muslim (465). 
Secondly: 
You should advise your 
    father a great deal and encourage him to pray and to offer the prayer in 
    congregation. You should tell him of the reports that speak of the 
    punishment for the one who does not pray, and tell him that prayer is the 
    foundation of religion, and the one who neglects it is subject to a warning 
    of a stern punishment, as Allaah says (interpretation of the meaning): 
“Then, there has 
    succeeded them a posterity who have given up As‑Salaah (the prayers) [i.e. 
    made their Salaah (prayers) to be lost, either by not offering them or by 
    not offering them perfectly or by not offering them in their proper fixed 
    times] and have followed lusts. So they will be thrown in Hell”
[Maryam 19:59]
And the Prophet  (peace 
    and blessings of Allaah be upon him) said: “Between a man and shirk and kufr 
    there stands his giving up prayer.” Narrated by Muslim (82) and he said: 
    “The one who does not pray ‘Asr, his good deeds will be cancelled out.” 
    Narrated by al-Bukhaari (553). 
And he said: “Do not 
    associate anything with Allaah, even if you are cut and burned. Do not 
    neglect any prescribed prayer deliberately, for whoever neglects it 
    deliberately no longer has the protection of Allaah. And do not drink wine, 
    for it is the key to all evil.” Narrated by Ibn Majaah (4034); classed as 
    hasan by al-Albaani in Saheeh Ibn Majaah. 
It was narrated from a 
    number of the Sahaabah that the one who omits a single prayer deliberately 
    until the time for it has ended is a kaafir – Allaah forbid. 
We ask Allaah to guide us 
    and you. 
And Allaah knows best.