Can a person who is Muslim in name only be given any part of the inheritance?
Question

                Is it obligatory for a muslim to follow the inheritence laws in the Quran?

 What if some of our family members are Kuffar ( muslims who dont pray, fast etc). 

I've heard people say that the inheritence laws in the Quran should only be applied when all family members follow them. Is this true?
Praise be to Allah.No part of the religion of Allaah may be forsaken because of differences in
      time, place or circumstances, whether it be the laws of inheritance or
      anything else. These rulings apply in all times and in every place, for
      Arabs and non-Arabs, male and female, rich and poor, nomads or
      city-dwellers; all of them are equal in this regard. When Allaah mentioned
      the laws of inheritance in Soorat al-Nisaa’, He said at the end of the
      aayah (interpretation of the meaning):
“(these
      fixed shares) are ordained by Allaah. And Allaah is Ever All Knower, All
      Wise” [al-Nisaa’ 4:11]
 Imaam Ibn
      Katheer said in his commentary on this aayah: this is an obligation which
      Allaah has enjoined and decreed. Allaah is All-Knowing and All-Wise, Who
      puts things in their places and gives each person what he deserves
      according to his own situation. “And
      Allaah is Ever All‑Knower, All‑Wise” [al-Nisaa’ 4:11].
      (al-Tafseer, 1/500).
 Then
      Allaah says, concerning the rulings and amounts of inheritance
      (interpretation of the meaning):
“These
      are the limits (set by) Allaah (or ordainments as regards laws of
      inheritance), and whosoever obeys Allaah and His Messenger (Muhammad) will
      be admitted to Gardens under which rivers flow (in Paradise), to abide
      therein, and that will be the great success.And whosoever disobeys Allaah and His Messenger (Muhammad), and
      transgresses His limits, He will cast him into the Fire, to abide therein;
      and he shall have a disgraceful torment} [al-Nisaa’ 4:13-14]
In
      this aayah, Allaah states that not implementing the shar’i rules on
      inheritance is a transgression of the limits set by Allaah, and that the
      person who does this will abide in Hell forever and will suffer a
      disgraceful torment.
You
      must realize – may Allaah bless you – that knowledge of the
      inheritance laws is half of knowledge, as some of the scholars said. Ibn
      Katheer said: Ibn ‘Uyaynah said: the inheritance laws have been called
      half of knowledge because all people go through this. (al-Tafseer,
      2/497).
Secondly:
If you
      believe that the person who does not pray is a kaafir and apostate –
      which is the correct view, and Allaah knows best – it is not permissible
      for a kaafir to inherit anything from a Muslim’s wealth, or for a Muslim
      to inherit anything from a kaafir’s wealth.
It
      was reported from Usaamah ibn Zayd (may Allaah be pleased with him) that
      the Prophet 
 (peace and blessings of Allaah be upon him) said: “A
      Muslim does not inherit from a kaafir and a kaafir does not inherit from a
      Muslim.” (Narrated by al-Bukhaari, 6383; Muslim, 1614).
Based
      on the above, those who do not pray cannot inherit anything from those who
      pray regularly, and those who pray regularly cannot inherit anything from
      those who do not pray.
Thirdly:
You should
      find out whether this person who does not pray has forsaken prayer
      altogether, or if he prays some of the obligatory prayers and neglects
      others. If the latter is the case, then he is not a kaafir, because the
      kaafir is the person who does not pray at all.
Fourthly:
From
      the above it will be clear that upholding the limits set by Allaah with
      regard to inheritance is obligatory in all cases, whether all the family
      members accept this ruling or only some of them do so, because the ruling
      of Allaah is fixed and definite. At the same time we should note that
      everyone who does not accept the ruling of Allaah is a kaafir who cannot
      inherit from his Muslim relative and his Muslim relative cannot inherit
      from him, if he dies when he still rejects the ruling of Allaah and is     still a kaafir. And Allaah knows best.