Son whenever he feels like it, or "has a feeling something is wrong" - he and I have a private network, so we know when the other needs us. Generally speaking, I hear from him, or get in touch once a month or so.
Foster-daughter texts frequently and phones more often than our son, but never really tells us her personal news.
Two nieces and nephew: when they want something, so contact has been minimal since my sister died. Sad, but I am not prepared to be the aunt /great-aunt who gives presents she cannot afford and gets nothing - not even a birthday text message in return.