What is the reason for the estrangement that led to the separation of the questioner and his small family from his relatives on the mother's side? And what is the sin of his children in this crisis?

My dear questioner, you will be rewarded for maintaining ties with your relatives, while your relatives are sinful for severing them. We advise you to continue maintaining ties with them unless it causes you harm, in which case it is permissible for you to cut ties with them to avert the harm.

Strive to keep your children connected with their paternal uncles and aunts, unless there is harm in this connection, in which case there is no harm in preventing them. This is your children's destiny, and a Muslim must know Allah's ruling, for Allah does not burden a soul beyond its capacity.