She died and left behind a husband, children and parents who are not Muslim

If the wife was Muslim, no one can inherit from her except her Muslim heirs, because of the reports narrated by al-Bukhaari (6764) and Muslim (1614) from Usaamah ibn Zayd (may Allah be pleased with him), according to which the Prophet (blessings and peace of Allah be upon him) said: “A Muslim cannot inherit from a kaafir and a kaafir cannot inherit from a Muslim.” 

Shaykh al-Islam [Ibn Taymiyah] (may Allah have mercy on him) said: The Muslims are unanimously agreed that a kaafir cannot inherit from a Muslim and a kaafir man cannot marry a Muslim woman. End quote from al-Fataawa al-Kubra (3/130). 

So her estate is to be divided as follows: 

The husband (which is you) gets one quarter, because of the presence of descendants of the deceased (the children). Allah says (interpretation of the meaning): “but if they leave a child, you get a fourth of that which they leave after payment of legacies that they may have bequeathed or debts” [al-Nisa’ 4:12]. 

The rest goes to the daughter and two sons, with each male getting their share of two females, because Allah says (interpretation of the meaning): “Allaah commands you as regards your children’s (inheritance): to the male, a portion equal to that of two females” [al-Nisa’ 4:11]. 

Her Muslim brother gets nothing, because he is deprived by the presence of a male child. 

Her non-Muslim father and mother do not get anything, as stated above. 

In order to divide the estate among the heirs, it should be divided into 60 equal parts, of which the husband gets 15, each son gets 18 and the daughter gets nine. 

If the wife was not Muslim, then no one can inherit from her except those who followed the same religion as her. 

And Allah knows best.