Court summons

Hi All, Can anyone please explain what can be done if in-laws refuse to appear in court on summons, instead only sends letters to court stating reasons for not being able to attend the hearing, everytime. I am aware that disregarding court's summons is considered as attempt of court and can be arrested to bring to the court, but what if in-laws only sends letters of excuse to courts absending hearings every and each time. I am referring to a 498a, 420, maintenance, etc. cases against in-laws. I fear they might only delay the court hearings requesting for next dates, for years, to escape consequences, to harrass the complainant. What can be done to avoid this legally? There should be a limit to not appearing in court hearings. Please help.