What should a young couple call their in-laws?
The Shulchan Aruch requires a Jew to honor his in-laws (Yoreh Deah 240,24). The rabbis point out that we learn from scripture that Moshe honored his father-in-law Yitro, and King David his father-in-law- King Saul (King David was married to Michal, the daughter of King Saul). The honor he must give them is, however, less than that which he must give his own parents. It is sufficient to treat them as respected "elders" (Ba"ch, Sha"ch, Pitchei Tshuva, Y'Chave Daat). The ban on calling one's own parents by their name stems not from the obligation to honor them- "kavod", but rather from the obligation to fear them "yirah", an obligation not extended to one's in-laws. It is permissible, therefore, to call in-laws by their names as long as this does not detract from the honor due them as respected elders, a factor that may vary from community to community and from family to family. If the in-law insists that he be called by a title other than his name, ignoring his request may be an affront to his honor even when it would have been permissible to call him by his name had he not made the request. In conclusion- if there is a request on the part of the in-law not to call him by his name one should do what is necessary within the bounds of common sense to avoid "machloket"- fighting and friction. If there is no such insistence and the children want to know if they are forbidden to call the in-law by his name, there is no such restriction as long as they do not detract from his honor as a respected "elder".