My Muslim family keeps eating haram food even though I tell them it is haram they say things like “Oh we already ate some might as well finish it” and when I tell them it’s haram it doesn’t phase them they just carry on eating it as if it is the best halal food on Earth. What do I do?
You should stop your family from consuming haram. By defiantly consuming haram food they are deserving of Allah's punishment and we are taught to protect our families from it:
يا أيها الذين آمنوا قوا أنفسكم وأهليكم نارا وقودها الناس والحجارة عليها ملائكة غلاظ شداد
O you who have believed, protect yourselves and your families from a Fire whose fuel is people and stones, over which are [appointed] angels, harsh and severe;
It also comes under Enjoining Good and Forbidding Evil (الأمر بالمعروف والنهي عن المنكر), which is a cornerstone of Islam, having been prescribed in the Quran in 3:104, 3:110 3:114, 9:71, 9:112, 22:41, 31:17 etc.
Leaving people to act as they wish and ignoring their wrongdoings is far from Islamic teachings, and there are stern warnings about this. We are told that such was the conduct of the previous nations which earned condemnation from Allah and from the Prophets:
لولا ينهاهم الربانيون والأحبار عن قولهم الإثم وأكلهم السحت لبئس ما كانوا يصنعون
Why do the rabbis and religious scholars not forbid them from saying what is sinful and devouring what is unlawful? How wretched is what they have been practicing.
لعن الذين كفروا من بني إسرائيل على لسان داوود وعيسى ابن مريم ذلك بما عصوا وكانوا يعتدون كانوا لا يتناهون عن منكر فعلوه لبئس ما كانوا يفعلون
Cursed were those who disbelieved among the Children of Israel by the tongue of David and of Jesus, the son of Mary. That was because they disobeyed and [habitually] transgressed. They used not to prevent one another from wrongdoing that they did. How wretched was that which they were doing.
Regarding how you should stop them from their wrongdoing:
That depends on what is effective and appropriate in that particular case: Inform and educate them, politely admonish them, scold them, use direct force to stop them (including wasting what they have of the haram food), threaten them, and then punish them or report them to the authorities.
It also depends on your own position and ability:
من رأى منكم منكرا فليغيره بيده فإن لم يستطع فبلسانه فإن لم يستطع فبقلبه وذلك أضعف الإيمان
Whoever among you sees an evil action, let him change it with his hand; if he cannot, then with his tongue; and if he cannot, then (only detest it) with his heart and that is the weakest of faith.
This is general and extends to your family, indeed your family is more deserving of being corrected by you, and you have greater responsibility with regards to them than to anyone else.
However if the offending family members are your parents, then you should only politely admonish them and avoid being more severe. That is because the requirement of respect and good treatment towards them takes precedence.
وقضى ربك ألا تعبدوا إلا إياه وبالوالدين إحسانا إما يبلغن عندك الكبر أحدهما أو كلاهما فلا تقل لهما أف ولا تنهرهما وقل لهما قولا كريما واخفض لهما جناح الذل من الرحمة وقل رب ارحمهما كما ربياني صغيرا
And your Lord has decreed that you not worship except Him, and to parents, good treatment. Whether one or both of them reach old age [while] with you, say not to them [so much as], "uff," and do not repel them but speak to them a noble word. And lower to them the wing of humility out of mercy and say, "My Lord, have mercy upon them as they brought me up [when I was] small."
Note: Be cautioned, this is my personal translation and may contain paraphrasing and mistakes
أجمع الفقهاء على أن للولد الاحتساب عليهما، لأن النصوص الواردة في الأمر والنهي مطلقة تشمل الوالدين وغيرهما، ولأن الأمر والنهي لمنفعة المأمور والمنهي، والأب والأم أحق أن يوصل الولد إليهما المنفعة ولكن لا يتجاوز مرتبتي التعرف والتعريف، وقد اختلف الفقهاء فيما يجاوز ذلك بحيث يؤدي إلى سخطهما بأن يكسر مثلا عودا، أو يريق خمرا، أو يحل الخيوط عن ثيابه المنسوجة من الحرير، أو يرد ما يجده في بيتهما من المال الحرام.
The jurists are in agreement that an offspring can take accountability of their parents. That is because the texts on commanding and forbidding are unconditional and inclusive of parents and others. Also the commanding and forbidding are for the betterment of whoever is commanded or stopped, and parents are more deserving that their offspring be of benefit to them. However the offspring must not exceed the level of informing and defining the matter to their parents. There is difference among the jurists on going beyond this in a manner which would incur the parent's displeasure, such as breaking musical instruments, spilling wine, tearing clothes of silk, or returning what they have in their home of unlawful property.
وذهب الغزالي إلى أن للولد فعل ذلك لأن هذه الأفعال لا تتعلق بذات الأب. فسخط الأب في هذه الحالة منشؤه حبه للباطل وللحرام
Ghazali's opinion is that a son can do this as these actions are not contingent on the person of the father, rather the father is displeased because of his love for what is wrong or forbidden.
وذهب آخرون إلى عدم جواز ذلك وهو مذهب الحنفية ونقله القرافي عن مالك وهو أيضا مذهب أحمد.
The others do not consider it permitted: This is the madhab of the Hanafis, and what is narrated from Malik and this is also the madhab of Ahmad.
قال صاحب نصاب الاحتساب: السنة في أمر الوالدين بالمعروف أن يأمرهما به مرة فإن قبلا فبها، وإن كرها سكت عنهما، واشتغل بالدعاء والاستغفار لهما، فإنه تعالى يكفيه ما يهمه من أمرهما (3) . وقال في موضع آخر: يجوز للولد أن يخبر المحتسب بمعصية والديه إذا علم الولد أن أبويه لا يمتنعان بموعظته
The author of نصاب الاحتساب says:
The Sunnah method of 'Enjoining Good' to parents is that one should command them once, if they accept it then well and good, and if they dislike it then one should become silent and engage in praying and seeking forgiveness for them, Allah will be sufficient regarding what worries people about their parent's matters.
At another place he writes: It is permissible for an offspring to give news of his parent's wrongdoing to an authority, if he knows that his parents will not cease because of his admonishment
ونقل القرافي عن مالك أن الوالدين يؤمران بالمعروف وينهيان عن المنكر ويخفض لهما في ذلك جناح الذل من الرحمة
وروي عن أحمد مثل ذلك، وفي رواية حنبل إذا رأى أباه على أمر يكرهه يكلمه بغير عنف ولا إساءة، ولا يغلظ له في الكلام، وليس الأب كالأجنبي، وفي رواية يعقوب بن يوسف إذا كان أبواه يبيعان الخمر لم يأكل من طعامهما، وخرج عنهما
Qarafi has narrated from Malik that the parents will be enjoined good and forbidden from wrongdoing, and in this matter they will be treated with humility and compassion.
And similar to it is narrated from Ahmad, and in the narration of Hanbal is that if he sees his father doing something undesirable them he should talk to him without being fierce or impolite, and not be harsh in his speech, for the father is not a stranger. And it is narrated from Yaqub ibn Yusuf that if the father drinks wine then do not eat food with him and separate yourself from him.
أما الاحتساب بالتعنيف والضرب والإرهاق إلى ترك الباطل، فإن الغزالي يتفق مع غيره في المنع منه حيث قال: إن الأمر بالمعروف والنهي عن المنكر ورد عاما، وأما النهي عن إيذاء الأبوين فقد ورد خاصا في حقهما مما يوجب استثناءهما من ذلك العموم، إذ لا خلاف في أن الجلاد ليس له أن يقتل أباه في الزنى حدا، ولا له أن يباشر إقامة الحد عليه، بل لا يباشر قتل أبيه الكافر، بل لو قطع يده لم يلزم قصاص، ولم يكن له أن يؤذيه في مقابلته، فإذا لم يجز له إيذاؤه بعقوبة هي حق على جناية سابقة، فلا يجوز له إيذاؤه بعقوبة هي منع عن جناية مستقبلة متوقعة بل أولى
As for being harsh with them, hitting them and forcing them to give up falsehood, then both Ghazali and the others are agreed that it is not permissible. They said: The command of Enjoining Good and Forbidding Evil is general, while the prohibition of hurting the parents is specifically in the right of both parents. Hence an exemption must be made for them from the general ruling. Hence there is no disagreement that an executioner can not not kill his father in the Hadd of Zina, nor can he himself enforce a Hadd on this parents, nor is he allowed to kill his disbelieving father in battle, nor is Qisas taken from a parent with respect to their offspring ... when he does not have the right to punish them for their past crimes by hurting them, then hurting them to prevent them from future crimes is impermissible to a greater degree.
Are they non-Muslims? Yes? Leave them be
Are they Muslims, but just don't care?! Yes? Leave them be.
Are they Muslims, but just don't know?! Yet do listen to your advice? Yes? Admonish them. Let me know. And that's it. You don't have to repeat it every time, because now they're taught/informed.
Forcing something on someone who knowingly disagrees or just don't care is useless.
If they ever asked (sincerely ie they didn't come with a charged question) you if something is haram, then answer them.
Generally when someone is doing something wrong/haram, we as Muslims tend to get angry and impatient, because what the person is doing is haram and despicable.
The best reaction is to convey what's right humbly and with a caring lovable voice — if we know they'll listen.
I can't find the hadith, but there was one that was saying something like: "give soft tazzakur to the wrongdoers". We should never be like: "You people!? You never get it! How many times do I have to tell you!? Don't you read Quran?! Shame on you, etc..."
Sometimes the best approach is a silent approach where you do the right thing openly...let others see and witness and just pray for them and hope they'll come towards you and do the right thing. You can also do istiqhfar for them. Give sadaqa in their name, etc.