All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.
First of all, we ask Allah to reconcile between you and your family, and we advise you to strive in this way. Reconciling between people is one of the great acts by which one gets closer to Allah; Allah says (what means): {No good is there in much of their private conversation, except for those who enjoin charity or that which is right or conciliation between people. And whoever does that seeking means to the approval of Allah - then We are going to give him a great reward.} [Quran 4:114]
Abu Ad-Dardaa’ narrated that the Prophet said, "Should I not tell you about what is better than the degrees of fasting, prayer, and charity?" They said, "Yes." He said, "It is to reconcile between people, for spoiling relations between them is the shaver (i.e. the destructive)." [At-Tirmithi] [The “shaver” means that which destroys one’s religion.]
You did not mention the reason why you deserted your sisters. In your previous question, you mentioned that they are bad, so if they do what displeases Allah, then you should advise them in a kind, gentle manner. You may also supplicate Allah to guide them, as Allah may guide them at your hands and you would thus earn a great reward.
The Prophet said to ‘Ali when he sent him to Yemen, "If Allah guides one single man by your efforts, that will be better for you than possessing an abundant number of red camels [a very expensive breed of camels which was considered as the most valuable property in the sight of the Arabs]." [Al-Bukhaari and Muslim]
Then, if they do not regain their senses, it is permissible to desert them. Deserting them depends on the benefit; if you hope that deserting them would be beneficial to them, then you may continue to do so, but if you fear that deserting them would make them more stubborn and more indulging in sin, then keeping ties with them is more appropriate. Hence, you should know that there is no sin on you in this case at all.
Now, if there is no legitimate reason for deserting them, then in this case, there is no doubt that it is obligatory to keep ties with them and it is prohibited to desert them.
The scholars have defined the lowest degree of keeping ties with kinship. An-Nawawi said in his commentary on Saheeh Muslim, "Keeping ties with kinship is of different degrees, some are greater than others, the least of which is to avoid the severing of ties and to keep relations by talking to them, even by saying 'Salaam' to them..."
As you know, customs and traditions have a great role in determining whether or not the ties of kinship are observed. So if the way you referred to in the question is considered as keeping ties in the customs of your society, then you are not considered as having severed the ties of kinship and you are not sinful; otherwise, you are sinful and have to repent. Please refer to the conditions of repentance in fatwa 86527.
In conclusion, it should be noted that remaining patient when being harmed by relatives and returning a bad deed with a good deed is of great reward. Abu Hurayrah narrated:
A man said to the Prophet "O Messenger of Allah, I have relatives with whom I uphold the ties of kinship, but they sever relations with me; I treat them well, but they mistreat me; I am patient with them, and they harm me." Thereupon, the Prophet said, "If it is as you say, then it is as if you are stuffing hot ashes [in their mouths], and you will continue to be supported by Allah against them so long as you continue to be like that." ["Stuffing hot ashes" means that your kindness to them in spite of their harshness is like feeding them hot ashes for the sin which they are committing by their wrong deeds].
Allah knows best.