How can one deal with one's only sister and her daughters, after the questioner felt a change in their treatment of her, and their concealing of life matters from her, which affected the way she deals with them?

Muslims should live in harmony and affection, for Allah Almighty says: "The believers are nothing but brothers," and the Prophet (peace be upon him) said: "The example of the believers in their mutual love, mercy, and compassion is like that of a body; if one part of it suffers, the rest of the body responds to it with sleeplessness and fever."

These meanings are even more emphasized among kin, for Allah has commanded maintaining kinship ties and prohibited severing them, as Allah Almighty says: "And fear Allah, through whom you ask one another, and the wombs. Indeed, Allah is ever, over you, an Observer."

It is imperative to maintain the bond between the two sisters and not allow any opening for Satan to sow animosity, for he is keen on sowing discord and strife. Allah Almighty says: "Indeed, Satan is an enemy to you; so take him as an enemy. He only invites his party to be among the companions of the Blaze," and the Prophet (peace be upon him) said: "Indeed, Iblis places his throne upon water; he then sends out his detachments... Then one of them comes and says, 'I did not leave him until I separated him and his wife.' So he brings him close to him and says, 'You are good.'"

It is good to understand that the nieces might conceal some of their circumstances, as they might have a reason for it. It is preferable not to inquire about what does not concern one, for the Prophet (peace be upon him) said: "From the excellence of a person's Islam is his leaving alone that which does not concern him."

If estrangement occurs between the two sisters, it might affect the relationship of their children. Therefore, it is recommended to strive to maintain the best possible relationship between the two sisters through visits, communication, and exchanging gifts, so that this may positively reflect on the children's relationship.