Is not meeting relatives except during the summer holiday considered a severing of kinship ties, and is inquiring about them through their children or neighbors considered maintaining kinship ties?

If, in your understanding, limiting visits to summer holidays is not considered a severing of kinship ties, then there is no harm in that. Maintaining kinship ties has degrees, the lowest of which is abandoning estrangement and maintaining contact by sending greetings. Whoever achieves the lowest degree of connection is not considered a severer of ties.